As compared to conventional sandy gas reservoir, the water saturation of a tight sandy gas reservoir has a higher effect on its identification in addition to its lower permeability. Moreover, no linear relationship is found to be existed between its porosity and permeability and confining pressure has a much more effect than that in the case of a conventional reservoir. The major parameter used in the classification of a tight gas reservoir for its evaluation is subsurface permeability, and porosity comes to the next, The major geological features are: (1) It is located usually in the centre of a sag in the sedimentary basin or on the slop of a transitional zone; (2) It is a lithologic trap usually; (3) It has a high gas column and with pay zones distribution in a fairly long interval; (4) It is usually abnormally high pressure. Large deltaic sand bodies should be taken as a major target for exploration with a depth of burial of <4000m, and attention should be paid to the parameter, water saturation.

The characteristics of oil migration and accumulation have been studied by the application of the chromatographic separation theory in this paper. It suggests that under a higher temperature weaker chromotogrophic separation of rock formation on the oil occurs, and is favourable to oil migration and accumulation) while under lower temperature strong chromatographic action occures and is unfavourable to oil migration and accumulation.

Based on the relations between the dissolution characteristics, the sequence of minerals filled in the pores and the homogenetic temperature of the inclosures in T ₁j ₂ ² carbonate reservoir of Huangcaoxia gas field in Eastern Sichuan, it is suggested that the reservoir had been subjected to dissolution for three times during the formation of the structure(during the uplifting of the fold). Its significance are: (1) the period of development of solution pores is in consistent with that of structure forming and the peak of generation and accumulation of the gas,which is favorable for the formation of gas reservoirs; (2) the superposition of the solution pores formed in three times improves the petrophysical properties of the carbonate reservoir; (3) the reasons that the structures control the variations of the petrophysical properties of the reservoir are explained; (4) the study of diagenesis is connected with the structure movement, which is favorable for directing the oil and gas exploration.

There are two characteristics in the Silurian buried hill oil pool and Cretaceous alluvial fan pool in Yaerxia Oilfield: (1) Both the buried hill and alluvial fan are resulted from the Y-509 fault,which are a pair of coexisting geologic bodies. When the basin boundery was controled by the fault, the coexisting geologic bodies were distributed along both sides of the fault as alluvial fan groups and their mountain chains, which is a favorable zone for the hydrocarbon exploration. (2) The alluvial fan which have developed for a long period is the fluvial deposits in a smaller area with great thick-ness,well-developed sandbodies, and variation in lithology.Therefore,it formed a reef-like and stacked lithologic trap which is rich in hydrocarbon in the alluvial fan apron. This kind of trap can be explorated as an important locality prior to other areas.

This paper demonstrates the application of AR spectral estimation to obtain the vertical transfer function of induction log, and to deconvolve the induction logging data with it for calibration. With a statistical model of formation conductivity distribution, this paper determines two constraints of the transfer function as: H(0)=1 and H(f)=h(-f). The vertical transfer functions of induction logging data in two wells located in different district are estimated by means of AR spectral estimation. Then, deconvolution as a calibration, are made by conjugate gradient method. Comparison of the data calibrated with core conductivity data from a well with oil base mud,7 late-rolog data and original induction data indicates that this calibration improves obviously the resolution and accurary of inducation logging data. In addition, scatter diagrams of induction logging data before and after the calibration shows that the calibration makes induction logging data closer to core data than the original ones.

This paper introduces the results of study and application in block wide watershutoff southwest chengdong oilfield, including the evaluation and improvement of chromium gel used in single fluid method, screening of the precipitatedtype plugging agent used in double fluid method, changing the chromium gel into a plugging agent which can be used in double fluid method, introducing the chrconium gel and using leak plugging agent etc. According to the programme of watershutoff,11267m ³ of above-mentione different plugging agents have been put into formation.During the test period, the annual increasing of water cut has been controlled to a level of less than 2% and increased of oil production has reached 3×l0 ⁴t.

This paper presents a two-dimensional (cross-section or plane) 2 phases (aqueous and oleic) multicomponent (seven components at least: water,oil, polymer, crosslinker, gel, monovalent and divalent cations) in-situ polymer gelation mathematical model. It takes the reaction of polymer-crosslinker and gel blockage of high permeability channel into concider action in addition to the phenomena involved in polymer flooding (viscosity, mobility reduction, residuel resistance,absorption, dispersion, inacces sible pores, rheology, salinity effect, etc). This model can be used to simulate water or polymer flooding and in-situ gelation process. Its application demonstrates that it is a very useful tool for studying different mechanisms, forcasting displacement performance and oil recovery, and designing the operation plan (such as kinds of their chemicals concentration, and quantity, injection strategy, operation parameters, etc) in such a technique. The examples in this paper give the results that the oil recovery by using gelation technique is better than that either by water or polymer flooding for a stratified reservoir with strong permeabilty difference between each layer, and the improvement of oil recovery depends on the depth of the blockage into the formation directly.

A new K-value compositional model for a retrograde condensate reservoir ispresented in this paper. The major physical phenomena and mathematical model used in the simulator are described.An application of both this K-value model and the compositional model based on the EOS to the example in SPE 4271 and a comdensate reservoir in our country are shown resulting in very good consistency. The new model which obtains K-values in a more effective way can cut down the time and the cost in the phase equilibrium calculation and simulation.

An experimental method for measuring steady-state three-phase relative permeability of oil, gas and water in acore samples has been developed in this paper. Oil,gas and water saturation measurement by microwave-weight techniques,relative permeability measurement apparatus and experimental procedures are involued in the method. Three-phase relative permeability of oil,gas and water for a number of water wet sandstone. core samples has been measured by this method in steady state condition. Results indicates that this method is valid to measure three-phase relative permeability of oil, gas and water.

On the basis of the pipeline parameters,gas qualities and operation data of Fu-An gas trunk pipeline, this article gives empirical equations used for calculation of hydraulic friction coefficient, pipeline efficiency and flowrate in the hydraulically smooth zone. The relations of pipeline efficiency versus flowrate and that of hydraulic slope versus flowrate are drawn. A comparison of calculated values with measured ones from the Fu-An and Zhongbadeyang pipelines showed a 2% deviation on the arrange and no any figure greater than 5%. How ever comparison of the values calculated with Weymouth equation gave a deviation between 200% and 300%, up to 500%. This paper indicates that the new empirical. equations can be used for the hydraulically smooth flow region and for calculation in the design of a new pipeline. The relations in the diagrams can be used for pipeline operation, scheduling of purge and detection of leakage.

This paper presents a new electrical analogous equipment,which has solved the problem of a compacted zone around the perforation and drilling damages around the wellbore. Under negative pressure there is no blocking up by perforation debris. The equipment is designed for the parameter range under negative pressure. The experiment was arranged and conducted with the application of mathematical statistics in terms of nine parameters: perforation penetration, perforation diameter, shot density, compaction thickness, compaction damage, perforation phasing peoforation model, drilling damage and damage depth.The advantage of this technique is less times of tests and simple date treatment.The regression equation can predict the effects of the nine parameters upon well production.The results derived from permeability theory are applicable to any homogeneous reservoir.

The residual stress may seriously affect the fatigue strength, initiation and propagation of cracks and stress corrosion of pressure vessels. The welding residual stresses in a floating roof 100,000M crude oil storage tank were measured in the field by means of the Blind Hole Relaxation Technique. The principle of measurement and arrangement of measuring points are described in detail in this paper. This distribution of welding residual stress was obtained on the most important parts of the oil tank where the load was the greatest. The residual stresses in the horizontal and vertical directions for fillet welds, longitudinal welds and circumferential welds in the oil tank were measured accurately. The results of measurement indicates that the residual stress is concentrated in the weld and decrease sharply with a slight departure from the fusion line of weld. The maximum value of residual stress in the weld is close to the yield strength of the parent metal, and the residual stress along the weld direction is much higher than that across the weld direction. However, as the fillet welds by manual arc welding on the oil tank root are made under the condition of serious transverse restraint,the residual stress perpendicular to the weld direction is also fairly high.

This paper proposes a kind of analysis of sinking performance while filling-in water in float laying of offshore pipeline and a calculation model of the pipeline on which wave and current act simultaneously. An approximate solution is obtained with Laplace transformation to handle the pipe on sea bottom and by utilizing weighted residuals method and Brown method of solving non-linear equations. Finally, an example is given to show the calculation procedure.

This article suggess a free surface boundary influence coefficient M in a sucker rod string, the partial surface defect is simplified to a partially elliptical surface crack. On the basis of an exact analytical solution of the stress intensity factor of an infinite elastic tension body with flat elliptical crack, the problem of a sucker rod string with partial surface defect is simplified to a problem of a round tension rod with partially elliptical surface crack. Assuming that the deformation of the surface crack in the round tension rod is a partial ellipsoid,the relation between M and center opening displacement Δ ₀ of surface crack mouth are obtained.It is called simply as a M-Δ ₀ equation. The coefficient functtion M (a/r, a/c) is obtained by using marking techniques in fatigue crack growth to delineate the different crack shanes, determining their corresponding displacement by experiments,computing the corresponding values M by M-Δ ₀ equation, and making regression on data M in different crack shapes. Thus we get an approximate expression of the stress intensity factor of a sucker rod string with partial surface crack. A comparison of the numerical values on the deepest point of corresponding surface crack shape with the results in literature shows that they are somewhat con-sistant to each other.

The sealing elements in an oil well packer are made of elastomeric materials with non-linear geometry and material behavior.The non-linear relation of the materials is generally expressed in terms of a deformation tensor with three invariants of in this paper, on the basis of the principle of stationary potential energy and total Lagrange formalation, an incremental non-linear mixed finite element formulations of large displacement and large strain have been developed for elastomeric materials.Four-node quadrilateral isopa rametric ring elements are used to analyze an infinitely long thick-walled cylinder subjected to internal pressure. The computed results agree very closely with the exact solution, and the procedure is effective and reliable. The computations of the displacements, stresses and contact pressures are given which shows that: (1) the sealed tube is compressed on the external wall in the upper corner to turn upwards gradually; (2) the stresses in the sealed tube are basically compressible; (3) there are certain contact pressures on the internal wall and external wall of the sealing elements.The findings are useful for the rational design of the elastomeric sealing elements.

The sealing ability of the cap rock is an important iactor in the formation and conservation of natural gas in a gas reservoir.Based on the results of study of lithology,thickness,and depth of burial of the cap rocks on Tertiary gas reservoirs,this paper gives a further study of the breakthrough pressure,median radius,concentrated pore size and its percentage,the amount of pores with a radius of less than 630,type of micropores distribution of the cap rock,3 grades of cap rocks are classified for their quantitative evaluation.The mechanism of the formation of a natural gas reservoir is demonstrated to give a basis for the understanding of the distribution of gas reservoir to promote future gas exploration.

According to organic facies-abundance,type and maturity of the organic matter,hydrocarbon source condition in Middle-Upper triassic,geochemical characteristics of natural gases and the relationship between natural gases and organic matter maturity of surronding rocks in Sichuan Basin were discussed in this paper.The author considers that there are only elementary hydrocarbon source condition in part of layers in part of areas,but maturity of natural gases is obviously higher than that of the surronding rocks,thus it will lead to a conclusion that gas is mainly come from the underlying Permian.According to the distribution and development of fracture systems,the possiblity of upward migration of natural gases is discussed also.This paper pointed out that more attention should be paid to the path of migration,so as to increase the success ful ratio of exploration and enlarge gas-containing regions.

Results of actual analysis of Permian,Triassic and Sinian tight gas reservoir rock demonstrate that it is characterized by thin irreducible water films,low irreducible water and high gas saturations.These results,combined with other data,such as those of adsorption hydrocarbons,inclusions,bitumens,pyrolytic chromatography,index of oil generation,capillary resistance etc.,demonstrate that large amount of primary natural gas in the tight carbonate reservoir which is hard to migrate is the origin gas in such reservoir,the source rock formation being the reservoir formation itself.The mechanism of formation of such gas reservoir is further discussed by an analysis of 3 types of such reservoir.

In this artical the characteristics of evolution development and of lower Tertiary in Bohai Basin was summarized and it is pointed out that the gravity flow sediments was widely developed and the lacustrine tempestite can be good reservoirs.It was considered that the new principle of straigraphy(verticle accretion and lateral accretion)will play an important role in petroleum exploration.Through the discusion of diagenesis of depositional sediments,a new view point is suggested about mechanism of formation of the pore space in a reservoir,it is considered that the petrophysical properties of reservoir is control led by both micro-sedimentary facies and diagenesis.It is pointedout that reservoir geology plays a more important role in petroleum exploration and development.

In this paper,the optical properties,origin and distribution pattern of vitrinite occurring in different kinds of organic rocks and oil source rocks are investigated in detail,and a preliminary classification is suggested in which vitrinite are divided into three types according to its origins hydrogenrich vitrinite(A),normal vitrinite(B)and reworked vitrinite(C).A quantitative discussion is made for the reflectance differances between this three types and their evolution pattern during thermal maturation.It is pointed out that the selection of maturation parameter for oil source rocks should depend on their organic petrological characteristics.In low mature stage,the reliability of vitrinite reflectance as a maturation parameter will increase as the organic type of the oil source rock becomes worse.However,in the over mature stage,the reflectances of the three types of vitrnite become gradually consistent,and all of them can be used as a maturation parameter.

In reference,it has been shown that the incoherence functions of GLOBAL(mark of schlumberger)is not necessarily a convex function.To improve the solution of optimum interp retation of well lags,a new model and algorithm is proposed in this paper.Simulation tests reveal that the new model has advantages ,not only in salving the problem of well logging analysis,but also in selecting the well logging series and evaluating the solutions.Some important indicators-data:esolution matrix, parameter resolution matrix and the confident region of the solution-can be provided in this method.

In this paper,a comparison of effective radius model and skin effect model as well as theirs pressure solutions and type curves are made.By the comparison,it is clear that there are some limitations in effective radius model and its pressure solutions,and some problems in indiyidual type curves.The comparison shows that the effective radius model as well as its pressure solution and type curves are better,and have more satisfactory values in practice.At the end of this paper,model sketches,pressure drawdown solutions,theoretical curves and practical example analysis are presented for comparing.

High quality perforation is an important project in well completion for the purpose of formation protection and damage prevention.This paper,based on the results of modeling of well perforation by means of an electric resistance network and those obtained by a finite element technique,gives a comprehensive analysis of the effects of various factors on well productivity,such as perforation parameters,perforation damage,damage during drilling,and anisotropy of the reservoir formation etc.The relative importance of various factors are analysed and they are presented according their relative importance.A regressive equation including the above factors and a corresponding nomogtram are presented.Thus it is easy and convenient to predict the well prodictivity with different combination the above factors,and an optimyzed design of the perforation parameters can be carried out easily also.This paper also suggests contents,mothod and procedures in volved in an optimum design of well perforation operation.Results of field application(in Huabei oil field)show that well productivity is increased by 15-25%.Practices show that a comprehensive and accurate evaluation of the well productivity after perforation,reasonable choice of perforation parameters and an optimum perforation design have a significant economical benefit and a high practical significance.

In this paper,an efficient finite element method is presented for a two dimensional,two phase nonliear model of polymer flooding The associated computer program is designed and a simulation using some data of a "five point well pattern was carried out.It is shown that polymer flooding can increase the production efficiently and greatly as compared to water flooding.But proper polymer slug size should be selected in view of economy.It is demonstrated that finite elment method can be used in the simulation of polymer flooding.

In DST,a long time build-up test is genarally followed by a short flowing period.By introducing the factor Fd,this paper presents a new mathe-matical model for the interpretation of the whole DST pressure history,with a consideration of the wellbore storage in the build-up period,which is taken as a continues flowing period of the slug flow.In addition,this paper presents a set of new type curves on the basis of the numerical solution of the model by finite difference method.Their application will eliminate some problems which commonly appear in the currently used methods.Finally,interpretation procedure is described in detail,and illustrated further by the examples.

This paper suggests an application of fuzzy mathematics in the production of flowing wells.A mathematical model for diagnosis of a production of flowing wellsona minicomputer is established.The computer program of the flowing system is compiled also.This technique can be used in production well performance analysis and well management.According to the results of diagnosis,measurescan be taken to improve the well production.This technique has been proved to be successful preliminarily in actual field production.

Rock cutting by a step ped bit has been studied with experimental stress analysis and is tested under atmospheric pressure.The results show that step ped bit cut rocks with tension and shearing,so this bit is more efficient than others.The force on the cutter is not well-distributed The width and height of each step and the width-height ratio are the major factors influencing drilling rate.

On the basis of mathematical and rheological analysis of stress and timedependent deformation of rock salt in deep wells,a new numerical method to calculate the mud density for penetrating salt formation is studied.As the nonlinear creep model of rock salt obtained under simulated stress and temperature conditions is taken into consideration,the method is more accurate and applicable.By using this method a series of curves of mud density vs.formation depth and temperature are plotted.The results are in fairly good agreement with the field data.

The dynamics of self-synchronous mud screen shaker with straight line trace are discussed.This paper gives the requisite conditions for a shaker board's linear movement and for vibration exciter's synchronous rotation and various factors affecting self-synchronization of two vibration exciters,thus providing a theoretical background for selecting rational parameters of a mud screen shaker.

Tetraoxyethylene nonylphenol ether and monoglyceride stabilized distilled water,man-made formation water/man-made formation oil emulsions and brine/North Sea crude oil emulsions have been destabilized by organic solvent-like systems.The two emulsion systems have the same tendency and similar efficiency of deemulsification.Among these destabilizers the best ones are fatty amines,followed by fatty alcohols.Fatty amines will react strongly with the surface groups on the interfacial film,while the medium-chain-length alcohols will destabilize due to a diffusion/partition mechanism.When the dispersed phase is man-made formation water,both mechanizms are weakened.With the preasence of wax particles,the efficiency of the amines remains practically unchanged while the efficiency of the fatty alcohols declines.The highest destabilizing efficiency is obtained when a fatty acid and a fatty amine is used tegether.In this case the interface will contain charged acid/amine complexes and the film will be too hydrophilic to protect oil-continuous emulsions.

Among the various loads of a drillpipe,the tension load is the major one,since it is large in quantity and it is acting during the entire process of operation.Therefore the drillpipe design,in particular in a deep well,generally is made in considering the tension load.There are two methods which may be used for determining the tension load in calculation,i.e.,the margin of overpull method and the safety factor method.However,there have been no definite rules of application of these two methods in drill pipe design.Then it has brought the inconvenience to the drillpipe design.This paper discusses the design of a drill pipe under tension,and presents a criterion and curves for selecting between the margin of overpull and the safety factor.The whole problem is thus settled in a fast and easy way.

Based on a large number of data and examples,tile present situation trends characteristics of world petroleum exploration have been summarized.By a comparison and analysis,this paper suggests three directions of petroleum exploration strategy in China: (1)The first target would be to look or giant and super giant oil anci gas fields infiarim and lunggar basin,as well as Easd-South China offshore area where have lame productive capacity may be expected during 1996-2020.(2) It isneeessary to look for stratigraphic and lithologic pools in the highly m attired East and Central petroliferous provinces of China in order to guaranteethe pruduction of 140×10 ⁶-150×10 ⁶t/yr during1991-1995.(3)To strengthen the exploration of natural gas rapidly,and to find out giant or moderate gas fields will be important channels for compeusation of oil.the coali ferous gas is as important as petroliferous gas.

In order to study the 6iogenic methane generated by subsurface orgonic matter,a series of biochemical fermenting test,investigation on anaerobic bacterium and the geochemical analysis etc.on some peat,nlud,core,brown coal and plant samples from different regicans have been carried out.Organic matters in quaternary sediments in Chaidanzu basin where a large amount of biogenic gas is accumulated has a high biogenie methane potential (BMP),a middle BMP in the plants,and in mud,and a low BMP in the peats and brown coals.The sdudies shown that:original BMP in all types of organic matter is correlated to the living things from wltich they are originatedrespectivlv and the ratio of water soluble organic matter in them,while for remaining BMP,it is related to the special geological environmentswhich inhibite the bioebemical fermenting and methane generatin of organic matters at surface or shallowly buried.

This paper introduces systematically the lab work for the determination of the diffusion coefficient of light hydrocarbon as well as the results obtained.Mathematic models describing the diffusion of light hydrocar boas from source rocks and that for natural gas in gas-pools through caprock have been established to study quantitatively the effect of diffusion on gas accumulation.The dynamic equilibrium principle in the migration and accumulation of gas is put forward with a hope to help the advance of gas exploration in our country.

Nearshore subaqueous fans develop in the lower Damoguaihe formation,consisting of innerfan,midfan,and outerfan association.Seven lithofacies and layer divisions have been identified and interpreted as to be high-and low-density terbidites and debrites.Nearshore Subaqueous fans have under gone a complicated diagenetic history.The diagenesis of Proximal fans is affected by meteoric burial,but the distal,faeies is mainly controlled by normal burial.The formation of dawsonites is a diagenetic event,relating to deep magmatic movement.Difference in the microfacies of nearshore subaqueous fans exhibits difference in pore types and pore geometries due to their diagenetic histories and mechanisms.

In this paper,frequency spectrum and cross power spectrum of full acoustic waveform from acoustic waveform logs are calculated.Investigation on the contiguous frequency band (consistant frequency band)in DPD method is carried out,which is used to determine the P-wave and S-wave slowness.It is pointed out that,if the difference of the moveout determined with the contiguous band and the moveout calculated with the shear wave arrivals is less than one cycle of shear wave,the computed slowness is resonable,otherwise it is not reliable.

For a better simulation of the natural degradation of source rock Kerogen under experimental conditions,pyrolysis experiments on two kinds of source rock samples from Xinjiang and Jilin were carried out by means of high pressure differential thermal analyser(DTA).The pyrolysis DTA Curves were obtained under a linear rise of temperature of 10℃/min and a pressure of 1~60 atm respectively.The pyrolysis kinetics were investigated with the endothermal peaks in their DTA curves using integral method and differerntial method on an overall first order kinetic model.The kinetic parameters were calculated.It was shown that the pyrolysis of kerogen was retarded by pressure,and some effects of pressure on the pyrolysis kinetics were also investigated.Furthermore,a pressure factor f was proposed,and a new pressure kinetic model was established.Results indicate a fair agreement between experimental and calculated data by using the suggested model.

This paper discusses the basic principle of the sonic array transmittingsonde(SATS).The path of the sonic wave travelling is long in the long sp-acing sonic logging,thus,the sonic signal received is fairly weak anddose not satisfy the need requirement of logging in practice.According tothe principle of the phase shifting,the sonic energy distribution of the son-ic beam transmitted by SATS is in a best direction angle.Thus,the receivedsignal of head wave is increased to a great extent.

In this paper a summary and classification have been made on the develop ment adjustment for a water-flooding sandstone reservoir,and three fundarnental principles at its high water-cut stage are put forward:(1) Cambinine the hydradynarnic method ii}ith the EOR method,ciopending mainly on the former.(2) Combining well pattern regulari}ation with an elaborate division of formation,depending mainly on the forme:.(3)Combining the "formation-dredging" with the "forrnation-plugging",depending maimy on the former.