The physico-chemical properties of heavy oils originating from the continental deposits are high viscosity, low sulphur and trace elements content, high non-hydrocarbon and asphaltene content, and low saturated hydrocarbon contents. The gas chromatograms of their saturated fractions exhibit high concentrations of iso-and cyclo-alkanes, and bicyclic sesquiterpane, tricyclic diterpane, rearranged steranes, and gamma-cerane in the terpene and sterane series have a stronger resistance to biodegradation than other biomarker compounds. The formation of heavy oil reservoirs is chiefly controlled by late uplifting of the basin, biodegradation, water-washing, and free oxygen oxidizing. In terms of their genesis, the heavy oil reservoirs can be divided into four types: the weathered-eroded, the marginal oxidized, the secondary migration, and the bottom water thickening. Having a close relationship with normal oil reservoirs, heavy oil reservoirs are mainly distributed longitudinally at the stratigraphically or stracturaliy higher parts, they all buried at a deph less than 2000 meters, and most of them are distributed regionally on the marginal parts of the basin and depression.

Based on a comprehensive analysis of data from large amount of seismic, well log and drilling in Langgu depression, this paper discusses the structural history of the depression and its evolution. In the period of sedimentation of the 3rd member of the Shahejie formation, the accompanying block faulting being tilted towards NW a series of structural zones developed with striks in NE direction, such as reverse drag fold, central graben zone...etc. By the end of the deposition of the Dongyin phase, because the tilting of fault blocks was changed from NW to north direction, structures trending in NWW direction were produced. Meanwhile, a distinct structure frame work with stack of those resulted in two periods had been formed. In order to expound and hold the origine of different structurAL zones and local structures, some simple and inexpensive laboratory simulation tests in clay models and correspounding numerical simulation by finite element method are carried out. The results from these two modelings show that structures in the southern part of the depression are mainly dominated by gravity slippage, while in the northern part, both gravity slippage and horizontal right-hand torsion dominated the structural styles.

Cangdong fault, 230 kilometer long, is a famous fault in east China. The middle section from Nanpi to Tanggu, 145 kilometer long is of petroleum geological significance. There are 110 seismic lines crossing through Cangdong fault. Texture of the reflection from fault plane shown in seismic profile can be divided into four type: (1) Spoon shaped, (2) Listric shaped, (3)Step shaped and (4)Scarp shaped. Their origin can be interpreted as follows: (1) Spoon fault was caused by either tensoshear stress or shear plane eroded by water. (2) Listric fault was formed from difference in dissolution caused by erotion of various Precenozoic rocks on upthrow block. Step fault was caused by slide of Precenzoic rockmass on uptrow block. Scarp fault was caused by upthrust of this basecment rock from uplift to depression. The stress pattern of Cangdong fault during Meso-Cenozoic Era shows a right-hand rotational feature. The Precenozoic paleogeologic map was constructed based on data from a limited mumber of exploration wells together with a large amount of seismic data. The map shows that Cangdong fault is situated on a paleozoic anticlinal ridge. The anticlinal core is situated between Xingji and Beitaoxian A half part of this anticline is situated on Cangxian uplift, with an other part inside the Cangdong depression. The axisl trends 22 degrees NNE approximatively and shows a low angle intersection with Cangdong fault. The width of Cangdong fault plane is in a range from 5 to 13 kilometers. An area of more than 1000 square kilometer is favorable for oil and gas exploration. Main trap types are as follow: (l)Basement rock buried hill on fault plane; (2) Rollorer fold on fault step, j (3).Nappe below fault plane; (4) Alluvial fan on fault scarp and (5) Remanant hill etc. Several decade of such traps have been discovered presently.

Deepenning well Wei-Key in 1964, industrial gas flow at "Denying Limestone" Formation (Sinian) in Sichuan Basin was obtained. Since then the old aged strata have been explored continuously, and one of the large gas fields in China was discovered Afterwards, migrabitumen freguently appears in drill hole and in outcrops. This paper discusses the geological conditions and the classification of the bitumen, including various parameters such as colour, luster, configuration, density, softening point, solubility, fluorescence and (DTA), valatile carbon ratio, carbon-hydrogen elements, carbon Osotopes and so on. These data are integrated with those from thermal simulation tests to give a genetic classification of the natural bitunen, as migrabitumen soft asphaltic, asphaltic, gilsonite, grabluation, albertite, impsonite and so on. They are the products from a series of petroleum evolution. This classification is simular to Jacb's (Migtabitumen, 1985) one. From the northern boundary to the center of the basin the soft asphalt and asphalt changes gradually into grabluation, albertite and impaonite. Natural gas in the basin are considered as thermal evolution gas. It corresponds to the evolution stages and is the decomposed products of liquid hydrocarbons. It is suggested that the moderate thermal evolution area in the basin ( R ₀<4～5%) is the favorable region for natural gas exploration.

On the basis of the author's practice for gas research, a comprehensive theory of gas diffusion and oil genesis had been offered to solve the problems about geochemical hydrocarbon prospecting. In addition to the derivation of Fick first law equation, it is pointed out that the using of the equation is not enough to solve the problems about the theory of geochemical petroleum exploration. The age of oil and gas generation and the time from the start of HC gas diffusion to the earth surface must be considered. If the time from the start of diffusion to present days is equal to or larger than the time needed from the start of HC gas diffusion to the surface, HC gas wight reach the sureface, and good result of geochemical exploration in this area can be expected. This paper has calculated the cases in several oil and gas fields, such as Daqing and Shengli oil fields. It is demonstrated that good results may be expected in Daqing Area, while poorer results may be exhibited in Shengli Area. On the basis of the theory in this paper, it is predicted prospecting in Kuramay and Nanyang oil fields may be good. Two practical examples are given, one is in northeast-China, the other in northwest.

Based on actual field data and a comparison with those obtained from theoretical predictions, this paper gives an evaluation on the development results of the water flooded L-reservoir, Laojunmiao Oil Field. The items discussed include utilization efficiency of the injected water, water-oil displacement efficiency, conformance factor and the ultimate water flooding recovery etc. It is demonstrated that actual value of water utlization efficiency is very close to that predicted from theoretical curves, the water-oil displacement efficiency and the conformance factor are 0.541 and 90% respectively, and the ultimate water flooding recovery way be as high as 48%. Modification on grouping of the development layers, in-fill well drilling modification on the injection pattern and the ratio of the numbers of injection to production wells and the selection of the rationale separate-layer injection and production techniques in the water flooding of L-reservoir are presented and their technical results are discussed.

In this paper, the oilfield injection-production system is regarded as a "black box" system. In view of systems engineering, the conception of an overall information predection model is presented. The POISSON CYCLE model and the LOGISTIC CYCLE model, preseented by professor Weng Wen Bo, are used to describe the process of the production and the water cut changes in the oilfield injection-production system, and are taken as an essential mathematic model. The parameters of models are given by using the generalized recurrence gradient algorithm for system identification used in the modern theory of control which was presented by Professor Han Zhigang, and then a complete mathematical model for predicting the oil production and water cut are obtained. As verified by results calculated using oil field data from the oil field both at home and abroad satisfactory results are obtained both in the data matching and preformance predition. The precision of the performance prediction by using dynamic parameters is even higher than that using the classical ststic parameters.

This paper discusses mainly the convergence and non-uni-queness of an improved automatically matching technique for well testing data interpretationan important interpretation technique in modern well testing. These problems give much trouble in the actual field application of this technique. Based on a homogeneous reservoir model, with the application of the method of system engineering, a pressure build-up curve can be divided into two sections according to the difference of sensitivity to the parameters charaterized by them. A new iterative process is used instead of the original one by means of a sectionally matching technique. Both results of theoretical analysis and actual application indicate that this technique will result in an improvement in the convergence and the uniqueness of the solutions. Principlly this idea can be generilized to the automatically matching techniques applied to the interpretation of the well testing data in case of more complicated reservoirs, such as reservoirs with double porosity etc.

A theoretical development is presented in this paper which provides a concise and accurate method of handing the drawdown analysis for variablerate case. In this mothod the curves of production variation are replaced by broken-lines istead of a steped lines. Eq (6) is deduced to analyse pressure drawdown performance, the X in Eq (6) is given by Eq (7), (14) and/or Eq (19) for one, two and/or three line-segments respectively.

In this paper, the effective radius of oil well is included in the insideboundary in the problem of flow of fluid in a reservoir, thus a new model has been built. Taking the wellbore storage and skin into consideration, an exact solution of the pressure distribtion in a homogeneous reservoir. In the case of an infinite outer boundary, a finite closed boundary and finite boundary with the constant pressure. Furthermore, this paper has described dimeusionless bottom draw-down and pressure derivative curves for both infinte and closed boundary reservoirs under constant well yield. These are equivalent to the type curves used in modern well-testing analysis generally. These type curves are more exact than those derived by Gringarten et al.

The method of calculating for three-dimensional Jet-Wake flow has been presented and used in computer-aided-design of a centrifugal pumps. Modification of a US made submersible pumps has been studied in detail. Prediction of performances of those two pumps by theoretical analysis has been verified by experimental results. In the modified design, pump head in one-stage is increased from 2.7m to 4m and efficiency from 55%to 64%. The length of onestage pump is reduced from 75mm to 65mm.

The causes of tooth fall-off of insert rock bit were analyzed through experiments. The geometrical condition of insertion of carbide tooth into the cone hole was derived and the methods of defining each physical quantity in the above expression were given. Mechanical criteria such as measures of press fit between carbide insert and cone hole were put forward, by means' of these results the critical condition of the magnitude of interference was determined. This work provides a theoretical and practical method of design for the carbide insert and cone body.

This paper describes the application of magnetic technique to the production and transport of petroleum since the advent of neodymium-iron-boron (Nd-Fe-B), a permanent magnetic material with high magnetic energy product, magnetizing treatment of crude oil was carried out by a cohesive strong ma.gnetic field, resulting in an average viscosity-reduction up to 40～55%, the transpoitability was increased by more than 10%, and the paraffin removed interval for an oil well was prolonged from 10 to 20times. A correlation of the energy of the strong magnetic field to the change in shear force was derived in accordance with the principle of energy transformation. It is considered that viscosity-reduction lies principally in the change of shear force in crude oii under the effect of the strong magnetic field.

The flowability of waxy crude oil from South China Sea under low temperature can be improved with a chemical treating agent. The addition of 150 ppm EVA complex greatly improved the flowability: pour point was reduced from 32℃ to 11.5℃, apparent viscosity lowered by 86.9% and yield stress at 14℃ lowered by 98%. The feed temperature, cooling rate, and the composition and structure of the treating agent which would affect low temperature flowability were investigated. The mechanism of improvement is discussed in the light of wax composition, carbon number distribution of normal alkanes and their susceptibility to EVA of different structures. Cocrystallization is likely to take place only when the ethylene chain in EVA is nearly equal to the normal alkane chain in the crude oil. The crystal forms can then be modified, leading to pour point depression and viscosity reduction.

Prediction of fatigue crack life of sucker rod with variable amplityde loading has been studied in the lighe of stochastic fatigue principle. Based on investigations from sucker rod manufacturer and oil field operator, sucker rod signals from 19 wells with good representation were gathered and the load spectra wave established. Nominal stress method, local stress-strain method and fracture mechamics techniques are used to predict the fatigue crack life in theoretical anlysis. Simulation tests with programmed loading were performed. Statistical data, theoretical prediction simulation tests have given consistemt life prediction with 99.9% probability of survival, from which the "Mark Life" of grade C sucker rod is thus given. Propesals for further research are also made in the paper.

More than 40 coaliferous gas pools and gas-bearing structures have been discovered in our country,mainly distributed in six basins,ie:Sichuan,Ordos,Bohai Bay,Songliao,Qiongdongnan and the East China Sea Basins,and in five series:Ordovician,Carboniferous-Permian,upper-Triassic,Jurassic-Cretaceous and Tertiary.According to the relationship between these gas reservoirs and coal seams,the coaliferous gas pools can be divided into three types,i.e.,"source and reservoir beds in the same formation","lower source and upper reservoir formation" and "upper source and lower reservoir formations".There are mixed gas reservoirs formed by both coaliferous gas and other type of gases in the basins with multiple source formations.Four primary factors of thire evolution and accumulation have been summarized in this paper by analysing basic geological conditions in the Known coaliferous gas pools.

Various types of sand bodies were developed in many faulted lake basins in the east part of China.This paper summarizes systematically the seismic reflection configurations of sand bodies such as alluvial fan,delta,channel sands,turbidites and so on.Alluvial fan,in terms of their distributions and reflection configurations,can be classified into four types:wedgeshaped fan against the cliff,mound -like fan near the cliff,fan parallel to the cliff and slope fan,including eight kinds of configurations,namely,cliffwedged,cliff-bead-string cliff-mound,reflection-free configuration parallel to the cliff,slope-wedge and slope-mound reflection configurations,etc.Delta can be grouped into elongated delta and fan delta two types.The elongated delta exhibits two progradational reflection configurations:low-angle sigmoid and tangent-oblique configurations.Fan delta exhibits three progradational reflection configurations:high-angle sigmoid,parallel-oblique and oblique configuration.Channel sand can be classified into semi-lens and linear sand body,including three kinds of reflection configurations.Turbidites are classified into two types which are associated with delta and alluvial fan having their own reflection configuration respectively.The distribution of these sand bodies has their specific regularities.Alluvial fan and fan delta are developed at the steep side of the lake basin;delta developed along the long axes of basins,small alluvial fan and delta developed along the gentle slope of the lake basin and associated with sand bars along the shore.Deep-water fans and lens-like turbidites are developed in the deep water environment of the lake basin.

From the view-point of geomechanies,by an application of the result of comprehensive analysis of the results from structural geological,geomor-phological,and hydraulic geological studies,combined with those from laboratery mechanical simultaneous studies and those from seismic and exploratory drilling,this paper discusses the regularities of the faulted deformation charac-teristics of the geotectonic faulting and the regularitics of oil and gas enrichment in various geotectonic system(or stractural blocks).It is pointed out that in those strongly compressional deformed structural systems those relatively gentle regions should be explorated first;while those regions with relatively concentrated stress should be explorated first in the relatively weakly deformed structural systems.Thus commercial gas reservoirs may be discovered.

The main type of the west margin tectonics belt of the Ordos massif is characterised by thrust nappe.The over thrust nappe consists of four parts:nappe system,front zone,outer front zone and autochthon.The structural belt consists of many major thrust faults extended north-south approximately.The fault plane inclined towards west and over thrusted towards east,with an over thrust distance of 20-40m.The fault plane mainly slided along the coal-bearing formation in Carboniferous system and Permian system,with high dip angle at the upper part,low angle at the lower part and it is approximately horizontal in the depth.Klippen are found at many places on the ground surface in the region.Because strikes of the main thrust fault is changed,the belt is divided into four section from the north to the south.Each of the sections has its own structural features.This belt is one the most favouravle areas for the exploration of oil and gas in Ordos massif due to its thick sediments,better source rocks and reservoir rocks,and the pressure of various types of traps.The key to the oil and gas exploration is the maturity of the source rocks and the preservation of the oil and gas.The author states that the autochthons and outer front zones have better preservation condition and higher maturity of the source rock.The autochthons of the Lousan-Majiatan section and the northern part of the outer front zone of structural belt are most favourable for oil and gas exploration.

The effects of polyelectrolytes such as silicates and phosphates on the dissolution/precipitation/redissolution of aJkylbenzene sulfonate in a multiva-lent cation aqueous solution have been studied in this paper.It turns out that,the addition of polyelectrolytes gives an increase in the sulfonate tolerance for the multivalent cation to a different degrees depending upon the concentration and the chelation of polyelectrolytes.Within the limits of chelation,as the polyelectrolytes concentration is increased,the sulfonate tole-rance of the maltivalent cation increases.The sulfonate tolerance of the cation in presence of higher polymerization degree silicate is more than that in the presence of silicate with lower degree of polymerization.A thermodynamic model is presented for the precipitation and redissolution of olkylbenzene sulfonate in multivalent cation aqueous solution based on the solubility product of the sulfonate precipitates and the theory of double electric layer.The presented model takes the effect of polyelectrolytes on the electrical double layer,the formation of "mixed micelles" in the sulfonate-cations system,the variation of micelle surface potential and the chelation of polyelectrolytes to cations and the introduction of the degree of association of the multivalent cation with the micelles into consideration.Reasonable agreement in precipitation boundaries between the results of calculations with this model and those from actual experiment for alkylbenzene sulfonate-calcium.chloride system is obtained with or without polyelectrolytes.

Original fluid saturation distribution in oil and gas reservoir has been given much attension by the scienticts and engineers engaged in petroleum exploration and development.Based on a comprehensive analysis of the data from the laboratory determined fluid saturation directly from the cores from the wells located in various parts in a reservoir in various petroliferous provinse in East China as well as their capillarity data from mercury injection,this paper demonstrates the regularities on the variation of the original fluid saturation in a petroleum reservoir,analyzes the factors affecting this variation;and discusses the factor to which attensions should be paid in the application of the mercury injection data to evaluate the original fluid saturation of a reservoir.

It has made perfect in this article the methods in calculating z-factors of natural gas by using Hall Yarborough's formula,an approximate equation of the "reduced" density of the optimum initial value is suggested.By this equation,y' can be determined so that the value of "z" can be determined in less than 5 iterations without divergence.This will give a convenience for the calculation of z by an electronic computer.

The change of curvature of the borehole of a directional well is teken place as the result of the action of side force on the bit.To solve the problem of a multi-stabilized bottomhole assembly by beam-column theory,it is considered as a multi-supported continuous beam-column.The present paper extends this method to that of its 3-dimensional analysis by resolving this complicated problem into two simple 2-dimensional ones to determine two components of side force which cause the changes of the angles of inclination and azimuth respectively.

This paper presents a computational method for selecting a better joint structure at the joints of FRP(fiber reinforced plastics or fiberglass) sucker rod string in design.B_y calculting two typical contact states of the joint structure the distributions of displacements and stresses at the contact surface of the joint structure under the action of the maximum operating load and the condition of running and pulling the sucker rod have been obtained.The calculated results show that different technical measures taken in two typical structures give rise to the same effects,i.e.the uniformity of the displacement and stress distribution and the improvement of the reliability of the structures.This is of great significance in the selection of FRP sucker rod joint structure.The use of finite element method in computation has the following advantages:adaptability,less computer time,easier convergence in calculation etc.,and the method is theoretically rigorous.The method presented in this paper might be applied to other contact problems in large engineering structures.

Three-dimensvonal vertical vibration of the sucker rod string,tubing and liquid column in the sucker rod beam pumping system has been comprehensively atudied in this paper,a new set of partial differential equations describing the movement regularity of sucker rod beam pumping system have been obtained,and numerical solution of the partial differential equations have been obtained with finite山fference technique in a manner of lineAR and non-linear analysis.This mathematical model is better theoretically than one-dimensional and two-dimensional models which take sucker rod string only or sucker rod string and liquid column(unanchored tubing) only into consideration,so it may give a powerful tool for predicting the dynamic parameters of a sucker rod pumping system and well site diagnosis can be also.

The mast and substructure of a drilling rig is studied in a system of mast-substructure-base-foundation system.Calculation of the Static stresses in the mast and substructure has been done with finite element method.The sink of the ground surface was calculated with both Winkler's model and limited compressibility model.Simplified treatment of all types of bases was proposed.Finally,a sample of systematic mast and substructure calculation was done with successive iteration.A special-purpose computer program for systematic analysis of mast and substructure was developed and practical calculation was compared with the results calculated with previous method.Valuable conclusions for design and research were given.

Simplified models of drilling rig hoisting system with and without rigidi body displacement of drilling tool are presented.Preliminary analysis of the hook load variation are given.Generally speaking,the dynamic load of hook decreases quickly in the beginning and slowly afterwards,and its frequency is also changing.The average hook load in the acceleration period during hoisting is greater than that in the following period.Results calculated for some practical examples coincide with experimental data.

The differential equations describing the lateral bending Coupled vibration of a partialy filled submarine oil pipeline system caused by liquid flow in and out of the pipeline are given according to the theory of coupled vibration of an elastic body and liquid:Solving the equations by the weighted residual method,an approximate solutions of the free vibration frequency of the pipeline in with coupled vibration is obtained.The limiting erosion length can be determined by the resonance condition.The results can be used in a fully filled submarine oil pipeline system also.

Fifty four samples of Tertiary source rock and crude oil from the western part of Qaidam Basin have been analyzed geochemically.Isomerization level of C ₂₉-sterane was taken as the maturation scale.We observed a whole evolutionary series from immature and lowmatured to matured and highly matured oils which correspond to the products at different evolutionary stages of the organic matter in source rocks.The wide distribution of immature oil and the existence of a whole series of maturation in Tertiary continental deposit basins in China have an important geochemical feature.The observation breaks through the limitation of the theory of generating hydrocarbon from kerogen.It has the practical significance in providing a scientific basis for forecasting petroleum resources by maturation classification.The oils already discovered in Qaidam Basin are mostly under matured,and exploration for oils of other evolutionary stages,especially the highly matured oil,is promising.

The hydrocarbon bearing structures distributed in different plate tectonics setting can be grouped into (1) convergent sedimentary basins in the west,(2) divergent sedimentary basins in the east and (3) transitional basins in the middle (Taihang mountain-Wuling mountain) according to the mode of plate movement.Based on the structural history,genetic mechanism,geometrical configuration and plate movement,the hydrocarbon bearing structures are classified into two types and six sub-types.The first type of gravity sliding structures in the sedimentary cover includes three sub-types: overthrust structure.rollover structure and diapiric structure.The second type of basement-controlled structures includes three sub-types: tensional fault block,compressional fault block and wrench fault block.The rollover structures generally occur in rift basins in the east part of China,overthrust structures lie at the frontal zones of orogens in the west and middle parts,and diapiric structures are usually in rift basins in the east part.Tensional fault blocks are mostly found in the east part of China and in compressional basins as well,compressional fault blocks mainly lie in compressional basins and transitional basins in the west and middle parts of China,wrench fault blocks can be found in the east,middle and west parts.Nearly all types of local structures in sedimentary basins all over the world can be found in China.However,those in China differ in their shape and genesis resulting from different geological environments.Especially in the complex basins,which experienced varying geological stress conditions,there occur transitional or mixed-type structures.

With respect to source material,maturation,accumulation and flowability,gas is more favorable than oil in forming hydrocarbon deposits.The wide occurrence of basins onland and offshore,abundance of coal resources,rich variety of paleolifts and traps,all favor the formation of giant gas fields However,complicated movement of plate tectonics in China since the late Paleozoic era resulted in poor reservoir properties and less favorable preservation,which can be the reason why no giant gas field is found in China.The author makes the following proposal: (1)pay equal attention to large basins and small basins,(2) lay stress on Carboniferous and Permian,(3)focus on the locations of paleo up lift superimposed with various traps,(4)turn to deep formations with improved geological and physical conditions,(5)explore for non-hydrocarbon gas.

It is commonly believed that Cangdong sag belt is a dustpan-like fault -depression with hydrocarbons migrating towards its gentle slope.Therefore,the ge tle slope belt has been emphasized in exploration,while the center and steep slope belt of the sag have been ignored.Seismic sections and drilling data made ia the last few years revealed the complexity of the interior texture of the sag,which is composed of both Pre-Tertiary basement uplifts and basement terraces with related covering traps formed since the Tertiary.The texture of Cangdong sag belt is related to paleotectonic settings formed before the Tertiary deposits and blockfaulting occurred since the Tertiary.During the Indosiniasn-Yangshanian stage,anticlinal uplifts in NE direction were formed in response to the squeezing of the Pacific plate northwestward.The upwarped axea roughly corresponded to the present Cangdong fault belt.A tension fault system was formed in the top of the uplift by compressional uplifting,and the strata were severely disintegrated.Starting from Tertiary,the top of the uplift slid down dne to a tension from east to west along the system,and then,it was draped by contemporaneous sediments to form the present Cangdong sag belt.Obviously,the basement of the sag is closely related to the sedimentary formations above it.The basement of the sag gentle slope corresponds to the eastern flank of the paleouplift and is composed of Mesozoic-Paleozoic strata.During the Eocene,it was tensioned.The overlying Eocene strata formed the northwestern flank of the central uplift belt of Huanghua fault-depression.The Pre-Tertiary strata pinched out downdippingly.while the Tertiary strata thinned updippingly by overlapping on the fault plane.This is favourable for the formation of basement fault block reservoirs and anticline reservoirs in the upper formation.The basement of the center of the sag corresponds to the top of the paleouplift,and was severely disintegrated.In some parts,there is a lacuna of the Mesozoic and Paleozoic.It was tensioned during the Oligocene,and overlaid by the Oligocene strata to form faulted benches with older formation in the high and younger formation in the low.This is favourable for the formation of reservoirs in older formation with oil from younger source beds.The basement of the sag steep slope is composed of strata of different epoches.With a very complicated relief,the overlying strata overlap on the fault plane all the way.It may form paleogeomorphic reservoirs in the basement formation and structural-stratigraphic reservoirs in the overlying formation provided that sealing and blocking condition is good enough in the updip direction.The northwestern flank of the paleouplift is a part of the present Cangdong uplift and the basement of Wen'an slope.The new understanding of Cangdong sag belt texture not only widens the field of exploration in the gentle slope,but also shows good prospect in the center and steep slope.

A new micromodel of porous medium made on a glass plate using photofabrication and etching techniques is presented in this paper,the pore structure of which is a reproduction of that of the reservoir rocks.The displacement experiments were conducted with oil and water under waterwet condition,and the types of connate water and residual oil,their trapping mechanisms were observed in detail.The experimental results confirmed that the irreducible saturation in the displacement of water by oil is controlled by multiple factors,but the heterogeneity of pore structure of reservoir rocks is the most important one.During the displacement of oil by water the snap-off and by passing phenomena occurred frequently wihch are the major factors affecting the trapping of oil in pore.Experiments were performed under the consideration of the relation of the displacing pressure existing in oil formations and the pressure gradient in waterflooding.

Finite element method has been used to study the flow characteristics of perforated wells and to investigate perforator penetration and damage mechanism in combination with core target experiments.Establishment of a finite element mathematical model for a core perforation and its numerical solution are presented in detail.The effect on productivity ratio and skin factor of depth of penetration,hole diameter,hole density,phase,format,damage depth,damage percentage,compaction zone depth,compaction perc entage,wellbore radius,drainage boundary radius,K _z/K _r ratio,bottom hole pressure,boundary pressure and production pressure difference is considered in the mathematical model.Grid sensitivity analysis ensures convergence and accuracy of calculation.An example is given to illustate the flow behavior of the core target,and the effect of perforating parameters on productivity ratio is analyzed.The table listed in API RP 43 is shown by calculation,electric modelling and core target experiment to be less reliable.Revision of these data will help evaluation of core flow efficiency.Compaction zone permeability can also be obtained by back calculation.

Partial differential equations for the case of an infinite homogeneous reservoir with a horizontal fracture are formulated in this paper where wellbore storage is considered.In order to solve this set of equations,Green's function of diffusivity equation not the source functions,are introduced and the horizontal fracture is taken as a uniform-source plane.The Green's function of a slab region is thus developed.The wellbore storage effect is considered indirectly by using a variable surface flow rate.With the help of Laplace transformation and Green's function,the solution of the equation is obtained in Laplace space and the relation between transient pressure and production time in this system is investigated,The conclusions reached in this paper are as follows: 1.Green's function could be used effectively to solve parabolic equations.2.The difficulty in taking wellbore storage into consideration could be solved by introduction of a variable surface flow rate.3.The dimensionless pressure could be obtained from its Laplace expression by numerical inversion of Laplace transform.4.The dimensionless Log-Log type curves commonly used in field practice are presented.5.The early-stage and long term behavior of fluid flow is analyzed An approximate analytical solution is proposed to analyze field pressure data.Furthermore,formulas describing flow coefficient,fracture radius,wellbore storage factor are presented.Gringarten's conclusions from the model of an infinite homogeneous reservoir with a horizontal fracture without wellbore storage is a special case of the solution presented in this paper.

This paper presents the results of chemical flooding simulation for different situations by using the model established in the preceding part (No.1,1988).The simulator has been verified by good consistence of calculated results with experimental ones,to have the powerful ability to describe practical problems and work normally.Various simulations were Then perfoimed under field conditions for studying the effects on the oil recovery of different factors (such as composition and size of the additive slug,rate of injection,additive dispersion and adsorption,gravity,reservoir heterogeneity,fluid compressibility,injection/production method).The application demonstrated that the simulator is a very useful tool for analyzing mechanisms,forecasting pilot study performance,making project feasibility study,optimizing injection/production conditions,defining the working scheme etc.

This paper presents a new mathematical model for a sucker-rod pumping system.in addition to the consideration of dynamics factors of the sucker-rod string,the new model also includes the compressible fluid equation which describes the dynamics of the fluid column.Four definite solution conditions suitable to field situation and a connecting condition for a tapered sucker-rod string are derived.The effect of fluid physical parameters,mechanical movement parameters and bottom-hole pump performance are considered in the model.A new mathematical method is used in the paper to solve the model.Both the theoretical analysis and field tests have shown the reliability and accuracy of the solution.The new model can be used to predict the condition of a pumping well at various patameters and the dynamographs of the polished rod and bottom-hole pump.

In boreholes of different shapes,the load-deflection patterns of the well casing will be different.In a crooked well with variable azimuth,a casing segment between two centralizers will be subjected to non-planar deflection,because the gravity and the axial load exerting on the segment no longer act in the same plane and the lateral force acting on the centralizers in the borehole will change accordingly also.Another important point is that the spacing between two centralizers should be determined by controlling the total eccentricity of the casing,which consists of both the casing deflection and the centralizer's compressive displacement to be below some specified value.In this paper the casing deflection is calculated with Rayleigh-Ritz energy principles,the centralizer's compressive displacement is calculated according to the actual lateral force.A biplanar deflection method is used to solve the space non-planar bending of the casing in the borehole with variable azimuth.The total casing eccentricity is obtained by using the displacement superposition principle.The equations for calculating casing centralizer spacing are established with the casing allowable eccentricity for each kind of borehole,i.e.,the straight inclined hole,(the crooked hole with constant azimuth,the crooked hole) with variable azimuth.Two groups of centralizer spacing plots are presented for reference and analysis.

In this paper,the dynamic loads on the screw in a screw-liner pair with cross-sectional profiles of hypotrochoid or epitrochoid type of singlescrewed hydraulic machinery have been studied.The engagement theory,specifically the exact theoretical expressions of the axial forces,overturning force and overturning moment,transverse force etc are given.The findings are useful in design and research of single-screwed hydraulic machinery.