From the current exploration situation,Bohai Bay Basin belongs to exploration muture basin.Till now,8. 579 billion tons has been proved in Bohai Bay Basin.But according to the analysis of resources estimation,overall amount of resource is about 19 billion tons.The proved rate is only 45%.Therefore,there is much work left to do. Now exploration is mainly focused on Shahejie Formation in Paleogene.This paper will discuss the relationship of Paleogene source rock with hydrocarbon trap,the relationship of tectonic evolution with hydrocarbon trap and the possibility of oil and gas trap in the deep source rock (including Paleozoic).The exploration strategy in Bohai Bay Basin should be "checking up any information in the upper layer(Neogene),progressive exploration and develop-ment of middle layer(Paleogene)and exploring the deep layer(Paleozoic)".

The current petroleum exploration activities in the Tarim Basin are mainly concentrated in the Mangar and Kuqa petroleum systems.Exploration practice proved that multidisciplinary study using seismic (seismic-structural interpretation, constraint seismic inversion,coherence calculation),logging reservoir evaluation,digital simulation on fracture distribution,production test and integrated geological analysis enables to identify the features of the carbonate reservoirs,facilitates to do lateral reservoir prediction and realize the oil and gas distribution laws and is a very useful method to do exploration in the carbonate oil and gas provinces.As for the complex high and steep structural belts,salt distribution areas,high geostress and mountainous surface in the Kuqa system,using the balanced cross section technique,fault-related fold theory and advanced seismic acquisition,processing,imaging and interpretation,as well as rapidly penetrating the huge salt interval drilling technique facilitates detailed and effective structural interpretation and oil & gas identification and may lead to significant exploration breakthrough.

By synthetically studying the petroleum geology features of Mesozoic & Paleozoic in southern China and reviewing the exploration history,this paper tentatively bring forward the studying method about evaluating the superposition or transformed basins and its petroleum system.The core thoughts are emphasizing to proceed the dynamic evolution studies of petroleum geology.Chiefly by the quasi-3D basin modeling deduces the spatio-temporal evolution,process of hydrocarbon yielding and intenstiy of hydrocarbon production or source quantity in distinct geological stages of chief source rocks.Through analyzing the past & existent oil-gas fields,we can sum up the rules of oil-gas fields formation or destruction.And the direction of oil-gas migration & accumulation can be deduced from paleo-tectonic analysis.It is studied that the dynamic evolution of chief Mesozoic & Paleozoic petroleum systems in southern China regarding the main stages of tectonic movements.Authors suggest the realistic targets of Mesozoic & Paleozoic oil-gas exploration in southern China are secondary and hydrocarbon-regeneration petroleum systems,and the existent primary petroleum systems are very few.The perspective regions to explore Mesozoic & Paleozoic oil-gas fields in southern China as frontier areas are NE Sichuan (the foreland of Daba mountain)and western cliffy anticline belts of Shizhu synclinorium,Funin-Yancheng-Haian-Xinhua-Baoyin area in northern Jiangsu Basin,Qianjiang-Xiantao-Paizhou-well Chacan 1 area in southern part of Jianghan Basin, southern Poyang Basin in jiangxi,and northern depression of Chuxiong Basin.This conclusion is already approved by discovering the Zhujiadun gas field in Yancheng sag of northern Jiangsu Basin and Kaixiantaixi oil-bearing trap in southern part of Jianghan Basin.

Hydrocarbon resource assessments are the bridges and ligaments among exploration,exploitation,decisionmaking and policy programming.The improvement,development,selection and applying of assessing methods determine the appraisal qualities and evaluating precision.The authors put forward the fundamental principles for hydrocarbon resource assessment.They are respectively the rules of genesis,dark box,resembling,feeblest factors, uncertainty,geological filtering,infinite approach and systematic analysis.They are the theoretic norms for ways and means for choosing,applying analysis and result discussing.The paper discussed briefly the mentioned basic principles.

In the basin modeling system,the function of geohistry model is to rebuild the depositional and structural histories of a petroliferous basin.There are two kinds of method of forward deduction and backward deduction in this model. "Forward" refers to the restoration of geohistory from past to present,e.g.,the technique of overpressure,which is applicable to normal-compacted formations;"Backward" refers to the restoration of geohistory from present to past,e.g.,the technique of backstripping,which is applicable to under-compacted formations.The advantage of backstripping is highly accurate while its disadvantage is not applicable to under-compacted formations because overpressure is not taken into account.On the contrary,the advantage of overpressure is applicable to under-compacted formations but low accurate.The combination of backstripping and overpressure,which is first proposed by the author,can consider the overpressure and ensure the accuracy.Its main idea is that from presently known basin conditions to deduce backward in time the geohistory of every individual formation with backstripping first,to deduce forward in time the overpressure of the formations,and finally to modify the backstripping results. For more accurate reconstruction,geohistory model should consider as many significant geological phenomena as possible,such as depositional hiatus,sedimentary compaction, undercompaction (overpressure),single-formation erosion,multi-formation continuous erosion,fault and paleo-bathymetry etc.Among them,the simulation of fault development history is the most difficult.The author is the first one to present the backstripping considering the fault development history.

The Hadexun uplift,discovered recently,is a large,wide,gently dipped nose-shaped one plunging northeastward,which located at the western Manjiaer Depression in Tarim Basin.It was mainly developed in the Upper Paleozoic and Meso-Cenozoic horizons,particularly in the Carboniferous.Analyses of tectonic evolution revealed that the Hadexun uplift was a part of the Lunnan paleo-uplift during the period of pre-Jurassic,which is an ancient one pitching southwestward,just opposite to the pitching direction of Hadexun uplift.The Hadexun uplift was not formed until the end of Triassic when the strong Indo-China tectonic movement occurred.Therefore,a preliminary form of the present Hadexun uplift appeared in the Jurassic and was more obvious in the Cretaceous.Nevertheless, it is only up to the Neogene that the Carboniferous strata in the western Manjiaer region were reversed from southwestward dipping to northeastward and the present Carboniferous uplift was finally formed.Being located at the ‘fulcrum' site in the course of the Carboniferous reversing movement,the Hadexun area has been a moderate high and relatively stable tectonically,which is extremely favorable to oil accumulation and preservation in the region. Therefore the Hadexun area is considered to be the most favorable exploration region in the west Manjiaer Depression.The newly found Hade 4 oilfield is just located at this area.

The wide area and extreme thick sediments of marine Lower Palaeozoic are well developed in northern and southern,and especially in the western part of China,Tarim Basin.The major petroleum source rock systems in the Tarim Basin,however,are disputed and debated for a long time.It is suggested in this paper that a global glaciating happened during the Middle-Later Ordovician when would be favored for accumulating and preserving of sedimentary organic carbon,depending on the positive shifts of stable carbon and oxygen isotopic compositions within the marine carbonates taken from two typical outcrop and underground sections.According to comprehensive studies including contents of organic matter,maturity indexes and sedimentary facies,a macro-evidence about the Middle-Upper Ordovician as a major petroleum source rock in Tarim Basin is proposed here.Meanwhile,the research shows that the possibility and prerequisite of Middle-Upper Ordovician as a major system of petroleum source rocks in the Paleozoic deposited and developed in Lower Yangtze and western margin of Huabei(North China)platform.

The source rock drilling cuttings from Xu ⁵ to Xu ¹(2530~3780m)of Upper Triassic were continuously sampled in West Sichuan Basin.The absorbed hydrocarbons in the cuttings were analyzed and studied.The generation and evolution of C ₄~C ₇ light hydrocarbons derived from terrestrial organic matter in this area were defined as three stages:cycloalkane,alkane and aromatic.The thermal evolution triangle of light hydrocarbons from a large number of experimental data became the important foundation for the correlation of C ₄~C ₇ light hydrocarbons between terrestrial condensates and terrestral source rocks,as well as the correlation among terrestrial condensates from different reservoirs(different maturity)in the same structure.The modification to Thompson's maturation indexes of condensates was suggested from the discovering of the reversion of heptane and isoheptane values with R _o reaching 1.18%,not increasing with maturity in the profile section.Besides,the hydrocarbon generation model of the terrestrial organic matter in West Sichuan Basin was established based on the light hydrocarbon generation stages and the geological characteristics:gas-cycloalkane condensate stage(R _o=0.55%~1.13%),gas-alkane condensate stage (R _o=1.08%~1.40%)and gas-aromatic condensate or dry gas stage (R _o=1.30%~1.40%).

According to the geological data of the Southwestern Tarim Basin,authors have restored the strata erosion thickness of the area by use of these methods which are the thickness ratio of the nearby layers,the change ratio of reference layer thickness,and combining with traditional acoustic transit time and the deposition rate.To restore the strata erosion thickness by the thickness ratio of the nearby layers is based on the characteristic which the deposit has the heritage and succession in the same tectonic layer,and according to the thickness ratio of completely preserved nearby layers and the thickness of underlying layers;To restore the strata erosion thickness by the change ratio of reference layer thickness is chosen a complete layer as the reference layer in the bottom of erosion strata of the calculation points,and the change ratio of reference layer thickness is regarded as the change ratio of the whole strata thickness.Because the seismic data has been adopted,the reference points are many and the reliability is increased.Based on the thickness data,the strata erosion thickness has been calculated almost in all instances with the far ranging adaptability.

Igneous rock distribute widely in Tertiary in the east of China and the igneous rock reservoirs have "small and rich" features which is important reservoir for extended exploration and development in old areas to seek potential reserves and enhance efficiency,especially,igneous rock screened reservoir.But because of the complexity of space distribution and forming features,high-efficiency techniques are key to achieve task during extended exploration and development.The typical features of igneous rock screened reservoir are studied and concluded in this paper on the basis of seismic T ₀ model and seismic interpretation model.In the practice of extended exploration and development of Gao 81 block igneous rock screened reservoir, auther made new discovery in the early,new progress of extended exploration in 1998 and a breakthrough of fine study in 2000,and production capacity of this block incerased significantly.Evidently,the process and study method of the exploration and development of Gao 81 are practical and typical for the farther exploration of eastern old area,expecially the progress of extended exploration and development of "small and rich" igneous rock screened reservoirs.

The accurate evluation of gravel-packed well-completion pressure of multi-layer reservoir is significant for us to deepen the understanding of microscopic mechanism of formations protection and develop production of oil wells furthest.On account of the unreasonableness of the current methods a novel method is brought forth.As to multi-layer reservoirs,each layer can be divided into three areas:area of gravel-packing,area of perforation and area of radial flow.Each area has its own governing equaiton and the solution is expressed by Green function.The well bore pressure and layer-rate is given through Green function in Laplace space.The pressure drop and skin factor is obtained also in each area.In the end,a case of two-layer reservoir is studied and the reasonable conclusions are acquired by applying our novel method.

Xin 47 block is a stratified and faulted reservoirs with high reserve abundance, in which the technology of zonal injection development was applied.Due to the influence of the heterogencity,the situation of water driving is non-equilibrium in the interlayer at the same well pattern.Since 1999,the composite water cut of Xin 47 block was higher than 90% and the conflict of the interlayer became aggravated.The original stratum of production and well pattern would not adjust to the demand of tapping potential production.Since 2000,the work of the fine reservoir description and the subdivision development had been done in Xin 47 faulted reservoir and achieved a very good result.After the work,the composite water cut was decreased by 3% and the rate of oil production was increased by 0.38% and oil recovery was increased by 5%.It is clear that the application of the technology of fine reservoir description and subdivision is feasible for a layered and faulted reservoir to increase the water injection recovery factor.

The application of horizontal well technology has become wider in the developing of oil field.However there is a problem in the current methods of horizontal well numerical simulation:most of them do not consider the fluid pressure-drop alone the horizontal well-bore.So,it makes a relatively great deviation between the actual result of developing process and the result of numerical simulation.To solve this problem,we set up a new kind of horizontal well numerical simulation model in this paper,which based on the vertical well black-oil simulation model.It considers the influences of 4 kinds of pressure losses when the fluid flows in the horizontal well-bore (including well friction loss,acceleration pressure loss,mixture pressure loss and weight loss).The numerical simulation program based on the model can also deal with the anisotropic formation.Because the relevant matrix is a "seven-diagonal sparse matrix with an attached column" when we consider the pressure-drop alone the horizontal well-bore,we develop a new mathematical method,which is called "partitioned matrix multiplication combined with preliminary treatment of conjugate gradient".The trial solution of this method has indicated a faster convergence rate.By the numerical simulation program,we correlate,compute and analyze the factors that influence the horizontal well production,pressure loss alone the well-bore and flowing bottomhleo pressure.According to the results,we can give suggestions to the optimum design of the horizontal well.

The study on Reservoir Cores Adsorption Isotherms Using Paraffinic Hydrocarbons is a theme which is of difficult,but of practical and theoretical values,and which also is the foundation of the study on the laws of phase behavior and percolation of gas condensate system in real gas reservoir porous media.The contents of this paper, which are scarcely reported up to now in literatures,are one part of the theme.In this paper adsorption isotherms of N ₂, CH ₄, C ₂H ₆, C ₃H ₈, nC ₄H ₁₀ and the quinary (N ₂-CH ₄-C ₂H ₆-C ₃H ₈-nC ₄) hydrocarbon mixtures in three reservoir cores named R ₁,T ₁and T ₂at temperature to 323.65 and pressure to 8.12MPa are measured by volumetric method.Forty-two adsorption isotherms with 516 measure points,data of mole percent of component of gas and adsorbed phase after adsorption equilibrium with 431 measure points,are obtained.The results of these experiments indicate:(1)the fact that hydrocarbons will be adsorbed by reservoir porous medium can't be neglected in a real gas reservoir;(2)more than 5 percent of reserves in a real gas reservoir would have been adsorbed only estimated from the measured absorbance;(3)the adsorption capacity of reservoir porous medium is limited by its own pore structure,rock composition, specific surface,and also by the number and mole percent of heavy ydrocarbon component; and (4)according to adsorption capacity of each component in the quinary hydrocarbon mixtures,from strong to weak,it is nC ₄H ₁₀>C ₃H ₈>C ₂H ₆>CH ₄>N ₂.

It is of importance to position finding of bit for orientational drilling.Specially it is essential to downhole closed-loop automated drilling and intelligent drilling in the future.This paper introduces a new underground positioning system and it's idea,content and reality.According to the realities of drilling engineering,it provides three new nuderground positioning systems-underground GPS, underground radar and underground CT.The principle and technical structure for the new type systems and penetration frequency has been discussed.Also we look forward a prospects to the applied perspective of new underground positioning system in drilling engineering and other engineering for the twenty-first century.

In this paper,the synthetic assessment analysis of multi-factors for risk of extended reach drilling technique is presented in order to set up the model of function evaluation coefficient systems and this model is solved by the model of function evaluation coefficient system and the science basis is provided for setting up the model in this paper.The relation among the risk and many factors is described in order to take up the foundation for solving the model by this risk evaluation model.An example shows that this method is available,it is made for evaluating and averting from the risk of extended reach drilling technique and a mathematical model to do easy is provided for engineers.

The paper introduced the design and executive situation of horizontal part in well Niu 102 in Santanghu oilfield.This is unprecedented in China that UBD (underbalanced drilling) technique with foam was applied in horizontal well.How to select the proper different pressure of UBD in the horizontal part of the well was discussed in this paper,as well the design of foam parameter.The success of this kind technique provides the basis and the reference for the exploration in similar oilfield.

The large centrifugal pumps are widely used as the waterflooding for oil production in the fields,stabilizing and increasing the production of the crude oil.Their most of working problems of the units are caused by the vibration faults.This paper discusses the vibration-signal-based auto-diagnosis technology and system for the centrifugal pumps on basis of fuzzy mathematics and puts forward the concept and method of Compound Knowledge Base (CKB) according to the structural features of pumps,which effectively overcomes the shortages of the traditional expert system.The detecting methods,characteristic parameters and fuzzy inference of the pump units are confirmed in this paper.And the corresponding system software is also developed.Application of the system to waterflooding pumps has obtained better results in oil field.

The paper deduces vapor-liquid-solid material balance equations which has their own characterization in line with the generic view about hydrocarbon phase behavior in oil/gas system and the method for characterizing asphaltene components.With three phase algorithm which takes asphaltene precipitation into account,the technique can model asphaltene precipitation quantitatively.Moreover,the paper puts forward the opinion that the incompatibility between asphaltene components and light hydrocarbons can be described with larger interaction coefficients. The paper also presents the calculation technique of reference fugacity,and the matching method to saturation pressure and amount of precipitated asphaltene through the example shown in the paper.

Wire-wrapped screen combined with gravel pack has been recognized as an effective practice for controlling the movement of sand particles from an unconsolidated reservoir into wellbore during production of oil and gas. However,the operation success rate of gravel pack is very low.Based on the analysis of the gravel packing process and mechanism of horizontal well,this paper has discussed the flow resistance in gravel packing horizontal well,and improves the Gruesbeck model by using two phases solid-liquid theory.A horizontal well gravel packing model that consider fluid loss to formation have been established.The effects of all factors on packing efficiency have been analyzed by the calculation results obtained from this model.The results are that (1) in some range,packing efficiency increases with the parameters,such as flow rate,fluid viscosity,the diameter ratio of tailpipe to screen.However,it is not good for gravel packing if these factors are too big.(2) The packing efficiency decreases with the increase of gravel concentration in injected liquid,fluid loss to formation and gravel size.The operation factors can be optimized,and the option design can be made more scientific and rational by this method.As a result,the successful rate of sand control can be enhanced.

The economic evaluation of play in the oil and gas basin is significant for the improvement of the return of exploration and development investment in the oil companies.The paper discusses the method and process about the foundation of reserve model,engineering model,production model and economic model in detail,also takes the resource economic evaluation for the nine plays in one of strata of a western basin.By the formation of the valuing map,the paper have optimized four plays of them,which are recommended as the prior targets in the investment decision of exploration & development.

Based on the synthetical analyses of the timing of trap formation,gas maturity and hydrocarbon inclusions,3 periods of the formation and filling history of natural gas reservoirs in Kuqa foreland thrust belts are discerned,i.e.the early-middle Kangcun period(17~10Ma),late Kangcun to early-middle kuqa period(10~3Ma)and late Kuqa to Xiyu period (3~1Ma).Among them the late Kuqa to Xiyu period is the major one for the formation of natural gas pools in the foreland thrust belts,in which the discovered Kela 2,Kela 3,Dabei 1,Yinan 2 and Tuzi 1 gas fields were formed.The Kangcun to early-middle Kuqa period is the critical moment for the formation of original oil and condensate pools.Nerverthless,those early oil and condensate accumulations were generally adjusted and even destroyed by the latter strong tectonic movements and/or the filling of natural gas of high maturity and over-maturity in the late Kuqa to Xiyu period.The remanined oil accumulations are mostly secondary reformed in this period.

The plutonic fault-42,shallow fault-Ⅰin culmination-2 in Lenghu-5 structure,plutonic Xiannan fault and shallow Xianbei fault in Nanbaxian structure play a principal role in gas pool forming in north edge of Qaidam Basin.According to geological analysis and mathematical estimation,the fault sealability in those two structures shows obvious diversity:the lateral sealability of plutonic fault is better than that of the shallow one in Lenghu-5 structure;the lateral sealability of shallow fault is better than that of the plutonic one in Nanbaxian structure.The vertical sealability in Lenghu-5 structure is stronger sealability than that in Nanbaxian structure in corresponding depth in different structure synthem.The vertical sealability of Xiannan fault in Nanbaxian structure is relative inferior,which stretch as channel-way of oil-gas from maturation period of oil-gas to peak-period of hydrocarbon generation.Xianbei fault is patulous lower and obturation upper which is adventageous to gas pool formation.

Huanghua Depression is a structurally complicated rift basin formed during Tertiary in Bohai Bay Region.Its pre-rift structural system,mainly generated during Mesozoic era,dramatically affected the rifting tectonics and the structural styles of buried-hills in Huanghua Depression.A ccording to seismic interpretations and tectonic analysis,Mesozoic tectonic deformation can be clarified into Indosinian and Yanshanian episodes.A complexes N-S trending strike-slipping fault and fold system in Huanghua Basin which developed during Jurassic-Cretaceous overprinted Indosinian anticlinorium and syclinorium.It formed the basic structural sketch of "relics" and "hybrid" buried-hill and made a great influence on the evolution of Tertiary faulted-block hills.Thus,Mesozoic tectonic events in Huanghua Depression can be treated as an most important factor for evaluating hydrocarbon bearing potential in buried-hills,due to their domination in buried-hill traps,reservoirs,oil types,and the scale of oil pools in Huanghua Depression.

The Shanke-1,a scientific research well,is the first well which penetrated the Triassic and encountered light oil in the Taibei Depression,Tuha Basin.Based on the analysis of Triassic oil-accumulating conditions,a study of organic inclusions and advanced thermometry,three oil-accumulating stages are identified for the Triassic pool in well Shanke-1.The first stage is in late Xishanyao of Middle Jurassic,forming a small oil accumulation with a low organic maturity.The second stage,or the main one,occurs in late Sanjianfang of Middle Jurassic,but the oil trapped in this stage has been oxidized into asphalt.The third stage,lasting from Late Jurassic to Early Cretaceous,has resulted in accumulation of light oil,forming a productivity in Shanke-1.In Taibei Depression of Tuha Basin,therefore,we should continue searching for non-oxidized oil trapped during the second stage,which will have a much higher productivity than that in Shanke-1.It is also emphasized that petroleum preservation conditions,together with source and reservoir rocks,have to be deeply studied.

Songliao Basin underwent active rifting in the Late Jurassic Huoshiling to Early Cretaceous Yingcheng (J ₃h-K ₁ych),followed by a post-rift phase in the Early Cretaceous Denglouku-Nenjiang(K ₁d-K ₁n)and a reversion phase in the Late Cretaceous-Cenozoic (K ₂-K _z).The Xujiaweizi fault-depression is a representative gas-bearing sub-basin in the lower part of Songliao Basin in the rifting phase.During the rifting phase,the two evolutive phases of Xujiaweizi fault-depression were found:the main faulting period in the Huoshiling-Shahezi (J ₃h-K ₁sh) along the NW-SE direction,and the asgging period in the Yingcheng (K ₁ych).In the end of K ₁sh,Xujiaweizi depression reversed.The resource (K ₁sh) deposited in the NW extending sub-basin.This discussing is of great benefit to defining the Later Mesozoic stress-field in northeastern China and to finding the new gas-field in the lower part of Songliao Basin.

The sequence stratigraphic units in Changtu Sag include three supersequences(SSⅠ,SSⅡ,SSⅢ),and the supersequence SSⅡcan be divided into two sequences(SⅡ ₁ and SⅡ ₂).Based on the tectonic movement and basin-filling sequence in Changtu Sag,the sequences are farther divided into lowstand system tract,expansion and contraction system tract of lake-basin.The system tracts are composed of depositional system of fan-shaped alluvium,fan-shaped delta,half-depth-lake and shallow-lake and lacurine swamp.As for an influence of episodic extension-form-basin,Changtu Sag has undergone two lake-overflow during rift-filling stage,meanwhile it filled concentrated strata of black-mudrock during forming expansion system tract of lake basin stage and it established two typical petroleum systems which are organic rock of coal-bearing series and lake-facies.

The northern edge in Qaidam Basin is one of the three hydrocarbon bearing areas in the basin.Its source rock is the early and middle Jurassic coal measures.Organic matter types of source rock are mainly type Ⅲ ₁ and type Ⅱ Kerogen,type Ⅰ ₂ Kerogen distributes only at some limited areas.By ¹³C nuclear magnetic resonance research on different types of Kerogen of Jurassic hydrocarbon source rock in the northern edge,the paper gives the chemical structure of the type Ⅰ ₂、Ⅱ、Ⅲ ₁ Kerogen in the studied area and the relative content of "oil potential C","gas potential C","aromatic C" in the chemical structure,based on which the paper evaluates the contribution of different types of Kerogen to the generation of oil and gas through quantitative analysis.The paper draws the conclusion that hydrocarbon-generating potential of the type Ⅰ ₂、Ⅱ、Ⅲ ₁ Kerogen decrease and their contribution to the oil generating also decrease and the ratio of oil or gas generated depends on the type of Kerogen.Type Ⅰ ₂ and type Ⅱ Kerogen generate mainly oil and typeⅢ ₁Kerogen mainly generates gas.

By considering all the involved processes of oil production,this paper presents optimum study and systemic methods of oilfield development planning,using prediction theory,optimization theory,economic evaluation method,comprehensive evaluation theory and computer technique.Especially,in order to meet various planning requirements three kinds of oilfield development planning models are set up and also resolved by non-linear planning method,they are minimal cost model for a given total oil production rate,profit and loss balance model and maximal profit model.In addition,because of the limits of five year planning model used widely,a year by year planning model is developed,based on the prediction model of flow rate regression and natural degression rate regression.Based on the study,a PC simulator of oilfield development planning is developed,which can be used for predicting oilfield development indexes、confirmming the optimal allocation of production structure in PetroChina level and production optimal allocation to all the oilfields determining comprehensive queue of oilfield development projects and the best investment structure.Recently the simulator was used for the 2000—2005 development planning of PetroChina with satisfactory results.

At the high water-cutting phase of oilfield development,based on ancient fluvial sandbody outcrop and modern fluvial sediment expericnce,according to fluvial sediment pattern and formative mechanisms,utilizing abundant well logging curves,the subdivision and correlation,reservoir description and deposition pattern were conducted for the PI ₂ ³ sand body in west of Lamadian-Saertu Oilfield,which is the end of large fluvial-delta sedimentation system of North of Songliao Basin in China.The formative type of PI ₂ ³ sedimentary unit is sand-braided river with far-resource and low curvature channel,which can be verified by rock-core and dynamic development data.All of them not only can be used to solve the questions of the subdivision and correlation of PI ₂ sand body,clarify the opinions on its formative type,but also identify the only sand braided river sedimentation in the Sapugao oil layer of the middle oil-bearing assemblage in Lamaxing Oilfield.The results above are applied to practice,which has high value in remaining oil analysis and development.

Underbalanced drilling has been more and more utilized to minimize problems associated with invasive formation damage which often greatly reduce the productivity of oil and gas reservoirs.However,in many underbalanced drilling operations,additional benefits are not seen due to the difficulty of safely controlling the bottom hole pressure difference.Damage due to poorly designed and/or executed underbalanced drilling programs can rival or even greatly exceed that which may occur using a well-designed conventional overbalanced drilling program.A method for calculating the bottom hole flowing pressure during underbalanced drilling has been developed which takes into account all important factors contributing to this process.This transient,one-dimensional multi-phase flow method is closer to the true than conventional ones which consider the constant formation thickness as an assumption during drilling.Taking into account the changes of the formation thickness in calculating the BHFP,in addition author put forward the original viewpoint that keeping constant gas invasive velocity is safer than the traditional one that keeps the constant bottom hole pressure.We can safely draw the conclusion that it is possible to calculate and control the volume of gas influx if the method discussed in this paper is used during underbalanced drilling.

During the depletion process of gas reservoir with abnormally high pressure,there is usually an inflexion on the P/Z Vs.Gp curve.Correctly predicting the P/Z Vs.G _p Curves feature is very important for gas reservoir developing management.This paper proposed an analytical method to study the abnormally high-pressure gas reservoir's depletion characteristics.Considering the gas and rock's properties variation with pressure in the mathematics model of a circle closed gas reservoir,the average pressure can be deduced by the analytical method and can be used to analyze the depletion characteristics of abnormally high-pressure gas reservoir.All the possible P/Z Vs.Gp curve's features have been discussed in this paper based on the deduced average pressure solution.The result shows that the depletion feature of the abnormally high-pressure gas reservoir is sensitive with the variation of rock's compressibility and gas's PVT and the related water.The P/Z Vs.Gp curve's feature maybe different for different properties,it can be one of a straight line or a protruding curve or a concave curve .This analytical average pressure solution can not only be used to study the depletion characteristics,but also be a theoretical reference for correctly programming the depletion strategies of an abnormally high-pressure gas reservoir.

The process of drilling mud filtrate invading into an oil/gas reservoir is related to invasion time after the bed was penetrated,hence the reading of a resistivity logging tool is a function as time.Prior resistivity inversion algorithms are based on an over-simple step-invasion model,so they cannot give a realistic invasion image,furthermore,the inversion results must be influenced by the ideal invasion model.The present inversion of time-lapse logging holds fluid-and formation-related parameters that control the dynamic invasion process in the model.Therefore,it is able to exhibit the dynamic characters of a realistic invasion process and provides more information for researchers to evaluate a reservoir.Since the present model is sensitive to the variation of saturation,mud property,drilling condition and so on,a reservoir can be evaluated through matching time dependent field logging data.Original water saturation(or true formation resistivity) and mud cake permeability are regarded as unknown parameters to be determined from the inversion routine.Field applications for dual-induction logging illustrate that the present model is a reasonable and efficient method for reservoir evaluation.

Low permeability reservoirs commercial development is usually obtained by fracturing stimulation.The development of low permeability reservoirs is different from that of normal reservoirs because of the appearance of hydraulic fractures.Severe heterogeneity usually exist due to the permeability anisotropy resulted from developed or tensile natural fractures in low permeability reservoirs.As a result,it is necessary to take into account the effect of heterogeneity of both hydraulic fractured and permeability while planing well pattern.This paper presents the research of inverted nine-spot pattern which is normally used in the development of low permeability reservoirs and modified inverted nine-spot pattern and rectangular pattern.It shows that higher oil recovery and economic efficiency would be achieved by adopting the rectangular pattern if the azimuth of hydraulic fracture is clearly known.

This paper revise the formula presented and deduce a new formula on productivity forecast of fractured horizontal well,applying potential function principles,superposition principle,and mathematical method for solving matrix,considering flow resistance and pressure drop in fracture.As an example,the productivity of fractured horizontal well in a low permeability gas reservoir has been tested by using this formula,and some useful conclusions have been drawn from comparing and analyzing some factors.These conclusions are instructive in designing fractured horizontal well for low permeability reservoir.

During the process of directional drilling,the direction of well trajectory and its change are key parameters to monitor and control a well trajectory.As an important part of monitoring and controlling a well trajectory,the path-correction planning is generally required to reach a desired direction at its target.According to the characteristics of directional drilling technology,a three-section profile with two planar turns and one straight line is constructed in this paper to solve the problem on path-correction planning with the given direction in theory,which lays a foundation for effectively monitoring and controlling a well trajectory.The solving process of the design method proposed in this paper is uniform convergent due to avoiding solving the constraint equations set.All of the formulas are theoretically exact solutions,so the universal significance,computational accuracy,stability and convergence have been fully guaranteed.This method can be widely applied to planning directional wells,horizontal wells,extended-reach wells and multiple target wells while drilling.

The method and formula of simplifying double bent PDM to equivalent single bent PDM is presented and the integrated equations applied to DKO and DTU are derived and a step equivalent method of simplifying double bent(mutibent) PDM to single bent PDM is provided.The difference and relationship between the deflecting force of bit and limiting curvature,build-up rate,etc in concept is discussed in this paper through limiting curvature method.These methods and results can be used to explain doubtful points of theory existed and to guide the design of structure and behavior of double bent(mutibent) PDM assembly in horizontal drilling.

The heavy organic substances,such as wax,resin and asphaltene will precipitate as a solid phase,causing serioius problems to operate the oil and gas fields,when thermodynamic conditions of temperature,pressure or composition are changed in the process of oil and gas production.A thermodynamic model of the gas-liquid-solid three phases equilibria is presented,combing an equation of state with a solution theory.A regular solution theory is used to account for the non-ideality of the solid mixture,and an equation of state describes both gas and liquid phase behavior.A wax precipitation calculation for a live oil system is conducted using the thermodynamic model.The calculation results demonstrate that the pressure has a greater influence on that wax precipitation.The effect of pressure on wax precipitation temperature is greater below the saturate pressure than the above saturate pressure.

In this article,combinating Bingham fluid's constitutive equation with momentum equation,the velocity distribution of Bingham fluid's flowing in the encircle pipe is obtained by means of dimension analysis,which is under the condition of laminar flowing.Moreover the effects of some parameters such as yield stress and pressure gradient on the velocity profile have been discussed:the difference of velocity distribution between Bingham fluid and Newtonian fluid increases with yield stress,the width of flow nucleus also increases with yield stress;as pressure gradient is smaller and the velocity profile becomes flatter,it means the width of flow nucleus increases.