Lithologic Reservoirs

By using 3D seismic data, log curves and core data, and in the light of principle of tectonics and sequence stratigraphic analysis, this paper studied the Lower Cretaceous sequence architecture, depositional systems and development characteristics of lithologic reservoirs in Beier Rift. Five super sequences（second order sequences）, corresponding to five rifting episodes respectively, and ten third-order sequences within super sequences 2 to 5 were identified. The second and third rifting episodes correspond to the Lower Cretaceous Tongbomiao Formation and Nantun Formation respectively, they are characterized by extensional tectonic movement, and fan delta depositional systems and sequences architecture in syndepositional fault slope breaks are developed. The forth rifting episode corresponds to the Lower Cretaceous Damoguaihe Formation, it is characterized by strike-slip tectonic movement, and fluvial delta systems and sequences controlled by syndepositional flexure slope break zones and fault slope break zones are developed. The fifth rifting episode corresponds to the Lower Cretaceous Yimin Formation, it is characterized by transition movement from rifting to depression, and fluvial and flood plain depositional systems and alluvial sequences are developed. Sand bodies of lowstand system tracts of sequences in syndepositional fault slope breaks of the Lower Cretaceous Tongbomiao Formation and Nantun Formation are favorable for hydrocarbon accumulation.

Quantitative evaluation for hydrocarbon transport ability of faults connectedwith source rocks and relation with hydrocarbon accumulation: An example from E d1 of Nanpu Depression

FU Guang，ZHOU Liang，AN Ligang

2012, Vol.24(4): 8–12 Abstract ( 514 ) PDF (885 KB) ( 663 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.002

In order to study hydrocarbon accumulation of Ed1 in Nanpu Depression, based on the study of influence factors of the mechanism and ability of hydrocarbon transport, combined with the evaluation method of hydrocarbon transport ability of fault, the distribution of faults connected with source rocks and hydrocarbon transport ability of Ed1 in Nanpu Depression were studied. The result shows that there are a lot offaults connected with source rocks developed in Ed1. The hydrocarbon transport abilityoffaults connected with source rocks in Ed1in Liuzan, Gaoshangbu, Laoyemiao, the east of Naupu 5 region, Nanpu 1 region, Nanpu 2 region and its eastern area, Nanpu 4 region and its southern area are stronger than that in other region, which is favorable for the hydrocarbon generated in Es3 or Es1-Ed3 source rocks migrated into Ed1 and accumulated there. At present, there are a large number of hydrocarbons found in theses areas, which proves the feasibilityofthis method tostudyhydrocarbon transport abilityoffaults connected with source rocks.

Sedimentary model since Paleogene in northern margin of Qaidam Basin

SUN Guoqiang， DU Zhongming， JIA Yanyan， ZHOU Fei， HAO Xiaomei， SHI Ji’an

2012, Vol.24(4): 13–18 Abstract ( 542 ) PDF (1391 KB) ( 507 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.003

Based on core observation, cast thin section, well logging data and analysis of sedimentary sequence of the Paleogene and Neogene in the northern margin of Qaidam Basin, Combined with field observations, we studied the sedimentary model in this area. The result shows that clastic rocks are developed in Paleogene and Neogene in the northern margin of Qaidam Basin, such as conglomerate, sandstone and mudstone, and the sedimentary facies are mainly of braided river, braided river delta plain, braided river delta front and shore shallow lacustrine depositional systems. Conglomerate of Paleogene has the characteristic of upright cycle, so it is a water immersion process, and in Neogene it mainly develops alternating deposits of megaclast and fine grained detrital rocks which show frequent hydrodynamic conditions change. Due tothe cyclical changes in precipitation, mudstone developed in megaclast deposit area at the basin margin, and middle-fine sandstone also exsited in the mudstone deposit area at the basin sedimentary centre. This alternatingdeposits ofmegaclast and fine grained detrital rocks can formperfect reservoir-cap combination, and it is favorable for the formation of structural-lithologic reservoir. The sedimentary model shows the process of sedimentary evolution since the Paleogene clearly, which can provide reliable geological evidence for the further oil exploration.

Microscopic pore structure characteristics of Chang 81 reservoir in Huaqing area

LI Changzheng， SUN Wei， REN Dazhong， ZHOU Shuxun， WANG Xiujuan

2012, Vol.24(4): 19–23 Abstract ( 504 ) PDF (671 KB) ( 429 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.004

Based on investigation of cast slices，high pressure mercury injection，nuclear magnetic resonance and constant speed mercury injection，this paper studied the microscopic pore structure and microscopic pore fluid characteristics of Chang 81 reservoir in Huaqing area. The result shows that the microscopic pore structure types of Chang 81 reservoir are complex, among which intergranular pore-dissolved pore combination type is perfect，with better connectivity，pore throat radius is larger，and the movable fluid saturation is higher. And this pore combination type is the advantage channel for fluid filtration. Pore throat type，pore throat connectivity，pore throat size and claymineral contents together affect the pore fluid occurrence and flowability. The pore throat size plays a main role，especially the larger throat has an obvious advantage in the improvement of seepage ability.

Reservoir characteristics of Ma₅ ¹⁺² sub-member of the Ordovician Majiagou Formation in Gaoqiao area, Ordos Basin

LUO Xiangjian， TIAN Jingchun， ZHANG Jinquan， CAO Tongsheng， DU Yuguo， ZHAO Ronghua

2012, Vol.24(4): 24–28 Abstract ( 511 ) PDF (1115 KB) ( 500 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.005

Based on cores, cast thin sections, scanning electron microscope, mercury injection data, this paper studied the reservoir characteristics of Ma 5 1+2 sub-member of the Ordovician Majiagou Formation in Gaoqiao area. The result shows that the types of reservoir rock are mainly of dissolved dolomite, mud powder crystal dolomite, followed by grain （sand clastic） dolomite and brecciated dolomite. The main reservoir pore types are mainly dissolved pores, intercrystal pores, intercrystal dissolved pores, followed by gypsummould pores and fractures. The properties of reservoir rocks are poor, the average porosity is 3.26%, and the average permeability is 1.2 mD.With strong heterogeneity, it is totally a low permeability and lowporosity reservoir. The study of reservoir characteristics can provide geologic basis for the further exploration and development in this area.

Study on sand body development model of He 8 member in Suxi X well block of Ordos Basin

FAN Lingling， SONG Rongcai， JIN Wenhui， WANG Yong，WANG Shu

2012, Vol.24(4): 29–33 Abstract ( 459 ) PDF (803 KB) ( 437 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.006

The internal architecture of sand body controls fluid flow, which influences development effect. Sand body development model of braided river channel ofHe 8 member in Suxi X well block was studied according to the existing reservoir sand body architecture research methods and based on short-term cycle comparison in a single stratigraphic framework. Sand body architecture types are classified into truncation style channels, complete channels and relatively isolated channels. The sand body morphology mainly manifests box shape and Christmas tree shape in the rising half cycle, and manifests finger shape mostly in the descending half cycle. In the cross section, the sand bodies which have overlapping phenomenon vertically and intertwined characteristics horizontally are obviously developed. Sand body of the same channel laterallymigrated to the west. The sand body distribution is characterized by a big ratio of width and thickness, small curvature and discontinued （effective reservoir sand bodies）. Four kinds of sand body development models of He 8 member in the study area were summarized as followings: strong migration of overlaying channel sand body, river intersection channel sand body, relative isolation channel sand body and weak overlaying channel sand body.

Reservoir characteristics of Chang 4+5 oil reservoir set in Nanliang area, Ordos Basin

XU Li， WANG Yiping, DUAN Yi， XING Lantian， WU Baoxiang， ZHANG Xiaoli

2012, Vol.24(4): 34–39 Abstract ( 491 ) PDF (1012 KB) ( 768 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.007

The Chang 4+5 oil reservoir set which is composed of Chang 4+52 and Chang 4+51 sublayers in Nanliang area in Ordos Basin is an important oil reservoir. Based on petrological and physical features, this paper studied the characteristics of Chang 4+5 oil reservoir set and evaluated reservoir properties. The result shows that the reservoir sandstone is compose of arkose and lithic arkose; the pore types are mainly intergranular pores and dissolved pores; the main throat type is fine to micro-fine throat and the reservoir displays high displacement pressure. It indicates that Chang 4+5 oil reservoir set belongs to ultra-low permeability reservoir. Sedimentation and diagenesis are the main factors of ultra-low permeability. Sedimentation controlled the distribution of reservoir. Compaction and cementation decreased the primary pores, while chlorite-cementation, dissolution and hydrocarbon emplacement play constructive role of the porosity building. Based on lithology and physical properties, the reservoir rocks can be divided into two types. The favorable reservoir should be in the subsea distributary channel sand bodies controlled by sedimentation.

Application of seismic sedimentology in the area with complex lithologies:A case from the second member of Shahejie Formation in Qibei Sag

HONG Zhong，LIU Huaqing，SU Mingjun，NIU Haiqing

2012, Vol.24(4): 40–45 Abstract ( 476 ) PDF (944 KB) ( 551 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.008

With the guidance of seismic sedimentology theory, the seismic sedimentology study was carried out in the Bin-4 oil group of the second member of Shahejie Formation in Qibei Sag based on the research of seismic lithology and geomorphology. According to the geophysical response features of complex lithologies, the log parameter inversion constrained by relative acoustic impedance was conducted to obtain lithologic data. With the help of logging and well drilling data, the stratal slices were interpreted. The result shows that log parameter inversion can be used to distinguish the complex lithologies. The source direction, evolutional history and reservoir distribution characteristics of the sandstone of delta-lacustrine depositional system in Bin-4 oil group were clearly delineated by a series of stratal slices produced under the isochronous stratigraphic framework.

Well logging evaluation method for hydrocarbon source rock-reservoir collocation and oil enrichment area optimization of low permeability reservoirs

SHI Yujiang， LI Changxi， LI Gaoren， LI Xia， ZHOU Jinyu， GUO Haopeng

2012, Vol.24(4): 45–50 Abstract ( 548 ) PDF (732 KB) ( 483 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.009

Chang 8 oil reservoir set in northwestern Ordos Basin is characterized by low permeability，complex controlling factors and distribution rule of reservoir parameters. So it has become an urgent problem for reservoir evaluation and production. On the basis of fine logging interpretation for wells，oil saturation distribution rule and its controlling factors were analyzed, and well loggingmulti-well evaluation technique based on multi-subject combination was applied to low permeability reservoirs. Thus the method for characterizing the degree of oil concentration and hydrocarbon abundance by using logging data was established, and the idea that the collocation relationship between hydrocarbon generating ability of source rocks and oil concentration degree of reservoir controls the distribution of rich oil gathered blocks was put forward. Based on the clue of source rock-reservoir collocation, the oil enrichment rule of low permeability reservoirs was studied and the oil enrichment areas were chosen. The study is important to evade the risks of quick productivity construction of low permeability reservoirs, and it can also accelerate the process of exploration and development and enhance the whole benefit.

Reservoir characteristics and diagenesis of Dongying Formation in L oilfield, Bohai Bay

HU Zhihua， SHEN Chunsheng， LIU Zongbin， YANG Qinghong， LIU Yujuan， LI Shuanbao2

2012, Vol.24(4): 51–55 Abstract ( 507 ) PDF (674 KB) ( 535 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.010

To ascertain the reservoir characteristics and the physical properties controlling factors ofDongying Formation is the premise of the efficient development in L oilfield in Bohai Bay. Based on core observation, combined with thin section observation, scanning electron microscope, cathodeluminescence and physical property analysis, this paper studied and analyzed the reservoir characteristics, diagenesis and pore evolution under the guidance of reservoir geology theories. The result shows that the sandstone of Dongying Formation in L oilfield has the characteristics of lowmineral maturity and textural maturity. The main diageneses are compaction, cementation, metasomasis and dissolution. The diagenesis roughly experienced early diagenetic A and B stage and late diagenetic A stage, and now it is in the late diagenetic B stage. The diagenesis has great effects on controlling the physical properties in the study area. During the pore evolution, the compaction and the cementation are destructive, while the dissolution is constructive.

Reconstitution of original lake basin during Triassic Yanchang stage and sand body genesis in the center of Ordos Basin

PANG Jungang， LU Tao， GUO Ji’an， LI Wenhou

2012, Vol.24(4): 56–63 Abstract ( 535 ) PDF (869 KB) ( 534 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.011

Based on large quantities of drilling, outcrop and core data, combined with field observation and laboratory study, the lake shoreline, deep lake line and the lake basin bed formwere restored. The result shows that the lake basin center of Chang 6 period is located at Zhengning, Ganquan and Miaowan area. Delta sand bodies are developed in northeast gentle slope break zone, braided delta and gravity flow （mainly turbidite and sandy debris flow） in deep lake are developed in southwest steep slope break zone, shallowwater slope break zone and deep water gentle slope break zone are mainly developed in the northeast, and deep water steep slope break zone is mainly developed in the southwest of the lake basin, with the center migrating to the southwest and then to northeast. Therefore, delta sand body is still the target of exploration in the future. Meanwhile, the exploration of sand body formed in deep lake and during flooding should be enhanced. The sand body distribution rule in the east gentle slope break zone is different to that in the west steep slope break zone, sowe should adopt a different exploration strategy for different areas.

Concept of seismic sedimentology and its application in continental rift basin

MIAO Shunde， LI Qiufen

2012, Vol.24(4): 64–69 Abstract ( 537 ) PDF (1403 KB) ( 513 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.012

Seismic sedimentology is a new marginal interdisciplinary subject following seismic stratigraphy and sequence stratigraphy. It is superior in the research of depositional systems and reservoir prediction and has obtained obvious results in carbonate oil and gas exploration. But there is fewapplication in continental rift basin.With the help of high resolution seismic data, abundant log data and geological data, combined with Luanping field outcrops, guided by seismic sedimentology theory, a 3D geological model of fan delta was established based on the research of high resolution sequence stratigraphic framework and sedimentary system in Nanpu Depression. The framework includes one secondorder sequence unit and four third-order sequence units in Dongying Formation. The third-order sequence units can be divided into highstand system tracts, transgressive system tracts and lowstand system tracts by the maximum flooding surfaces and the first flooding surfaces. The sand bodies are large of scale in highstand systemtracts, which are the most favorable reservoir; while they are smaller relatively in lowstand system tracts, forming good reservoir-cap assemblages with shales in transgressive systemtracts. According to the structural setting and the three-dimentional geological model, guided by seismic sedimentology theory and research thought of well-seismic mutual feedback, it is considered that fan delta systemis the main depositional systemwhich is forming by several distributary channels, and thin layer lacustrine mudstone deposits between underwater distributary of channels.

Prospect prediction for shale gas resources of the Lower Paleozoic in Sichuan Basin

LUO Jian， DAI Hongming， SHAO Longkang， WANG Wei， LI Nan

2012, Vol.24(4): 70–74 Abstract ( 559 ) PDF (773 KB) ( 520 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.013

Based on the theory of petroleumgeology and geochemistry, this paper analyzed the development and distribution of the black clay shale in organic matter in the Lower Cambrian Qiongzhusi Formation and the Lower Silurian Longmaxi Formation in the Lower Paleozoic in Sichuan Basin. Four indicators including shale thickness, total organic carbon, organic matter types and maturity were applied to evaluate the shale gas resources in Sichuan Basin. The result shows that Qiongzhusi Formation and Longmaxi Formation have thick mud shale depositions, high organic carbon content, favorable organic matter types and very important post mature condition. So, it is concluded that this area has abundant shale gas resources. It is also pointed out the favorable exploration zones in the study area.

Application of wavelet analysis and grey system theory to sedimentary microfacies identification: An example from Chang 21 reservoir in the Fengfuchuan Oilfield, Ordos Basin

YANG Jiao， LIU Tao， BAI Yaowen， LI Na

2012, Vol.24(4): 75–79 Abstract ( 549 ) PDF (668 KB) ( 538 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.014

Because of complex geologic characteristics of Fengfuchuan oilfield, it is difficult to identify sedimentary microfacies by conventional approach. In order to solve this problem, wavelet analysis technique was used to carry out stratigraphic division and establish stratigraphic sequence. Based on the grey system technique, the evaluation parameters, criterion and weight coefficient which are suitable for the study area were chosen to identify sedimentary microfacies. The result shows that the first using of wavelet analysis and grey theory to sedimentary microfacies identification in Fengfuchuan Oilfield achieved good results, and it provides a feasible method to sedimentary microfacies research and can service for development adjustment of oilfield.

Application of rock physical parameters in block Su 59

LIU Xiaopeng， OUYANG Cheng， PENG Yu， HE Kui

2012, Vol.24(4): 80–84 Abstract ( 532 ) PDF (779 KB) ( 662 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.015

Reservoirs in block Su 59 of Sulige Gas Field are controlled by sandstone distribution and physical properties, with complicated gas-water relation. So it can not identify reservoir and fluid effectively by using traditional acoustic impedance inversion method. Through detailed rock physical parameters analysis, the elastic parameter combinations sensitive to lithology were found out, and extensive elastic impedance （EEI） model was established. EEI curves which have good relationship with natural gamma ray, porosity and water saturation were used to reflect lithology, porosity and oil-bearing ability. It is meaningful for elastic parameters inversion with pre-stack seismic data and reservoir and hydrocarbon distribution prediction.

Application of seismic inversion technique based on model to reservoir prediction: A case study from Xishanyao Formation in Niuquanhu Oilfield

XU Ying，QIN Xinping，WU Di，TAO Changzhou，PAN Youjun，ZHAI Yamei

2012, Vol.24(4): 85–89 Abstract ( 508 ) PDF (1099 KB) ( 579 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.016

The reservoir ofXishanyao Formation（J2x） in Niuquanhu Oilfield is characterized by lowporosity, lowpermeability, lowpressure and strongheterogeneity, soreservoir prediction is particularlyimportant. Through contrast and analysis of well logs, natural gamma ray curve and sonic log curve were selected to build up a sonic-dimensional pseudo-acoustic curve, and broadband constrained simulated annealing nonlinear global optimization inversion method was applied to carry out reservoir prediction. Through comparing three degrees of constraint of logging data（① 10% seismic and 90% logging, ② 30% seismic and 70% logging, ③ 50% seismic and 50% logging）, it is found that the inversion result from using 10% seismic and 90% logging is of the highest accuracy. It shows that using seismic inversion technique based on model can obtain high-resolution impedance information, and effectively distinguish reservoir fromnon-reservoir. According to the comparison between predicted and actual drilling results, the error causes and problems were analyzed.

Application of geological modeling to geosteering in Sudan extended-reach horizontal wells

WANG Libin， DUAN Xianyu， ZHONG Wei， LIU Xun， LI Chunhua

2012, Vol.24(4): 90–92 Abstract ( 623 ) PDF (1099 KB) ( 630 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.01

Palogue oilfield is a complex fault block reservoir under complex geological situation with complicated oilwater relationship. There is high geological risk while horizontal well was proposed in this oilfield. We applied threedimensional geological modelingmethod and conventional geosteering technique to solve this problemin Palogue oilfield in Sudan, and made full use of LWDdata to rebuild 3Dgeological model. The result shows that the veracity and efficiency were increased and high drilling footage was obtained by using this newgeosteering technology.

Single sand body modeling techniques and application:A case study from a block in Huabei Oilfield

WANG Donghuan， HUANG Sijing

2012, Vol.24(4): 93–98 Abstract ( 578 ) PDF (722 KB) ( 449 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.018

The prediction of single sand body morphology and distribution characteristics is the main contents of fine reservoir description.The model established by using conventional stochastic modeling techniques is greatly different to the actual reservoir, so it is difficult to predict the distribution of oil-bearing sand body. Using the data from the late development and three-dimensional geological modeling techniques to describe the distribution characteristics of a single sand body in three-dimensional space and to establish accurate three-dimensional geological model is one of the key issues to solve the oil and gas field development in late period. Taking a block ofHuabei Oilfield as an example, we discussed the implementation and practical application of modeling techniques to a single sand body by conventional stochastic modeling. The result shows that a single sand bodymodel can not only clear characterize reservoirs within the multi-sand body superimposition, but also reveal single sand body distribution and thinning out in the three-dimensional space, which express the fully understanding of the geological research, providingmore convenient and reliable data for oil and gas field development, especially suitable for the late stage of development with the high frequencywell network in the scale of single sand body.

A quantitative modeling method for fault-related fold and its application

WANG Yanjun， WEI Dongtao， PAN Jianguo， LIU Zhenhua， ZHANG Han， LI Linxia

2012, Vol.24(4): 99–103 Abstract ( 530 ) PDF (822 KB) ( 466 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.019

Due to the complexity of surface geological condition and subsurface structure of the thrust belts of foreland basins in central and western China， the qualities of seismic data imaging are generally poor. In view of this situation， a quantitative tectonic modelingmethod was put forward. The techniques such as seismic wave forward modeling, balanced geologic section numerical simulation and structural physical simulation were applied to establish the final quantitative model. The tectonic deformation characteristics were analyzed from the aspects of the amount of deformation， deformation mechanism，deformation time and deformation process. The proposed method was applied to determine the geometry and kinematic structural parameters in Dushanzi anticline in southern margin of Junggar Basin， and good results have been achieved.

Application of fuzzy clustering analysis to recognition of reservoir seepage media

ZHOU Ying， TANG Hai， WU Chengmei， LU Jianjiang

2012, Vol.24(4): 104–107 Abstract ( 379 ) PDF (498 KB) ( 400 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.020

Seepagemedia recognition is the basis for the study on reservoir. This paper took the Huoshaoshan Oilfield as an example, studied the relationship between seepage media and dynamic characteristics of production, selected dynamic production parameters closely related to the seepage media, and made a detail analysis of seepage media by fuzzy clustering analysis. The result shows that fuzzy clustering analysis is scientific and rational and it has an important significance in researching seepagemedia.

A simplified model to predict wellbore fluid temperature in consideration of unsteady state heat transfer in formations

ZHONG Haiquan， LIU Tong， LI Yingchuan， ZHU Yabing， LIU Ximao

2012, Vol.24(4): 108–110 Abstract ( 454 ) PDF (274 KB) ( 633 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.022

Wellbore fluid temperature distribution is the important foundation of oil/gas well test and analysis, production optimization design and performance analysis. Due to its complexity and partly unavailable accurate data, the theoretical temperature prediction model is of little application. Based on the previous research, a newmodel was constructed by taking the unsteady state heat transfer in formations into consideration. In this way, the uncertainty of wellbore fluid temperature calculation due to overall heat transfer coefficient could be avoided. The example shows that the prediction of this newmodel is better in both wellbore fluid temperature change under different circumstance and accurate time length required to reach stability.

Research and application of gas huff and puff of deep heavy oil in the Tuyuke Oilfield

ZHAI Yamei， YAN Yupu， WAN Yongqing， LIU Yuanping， XIA Zhengchun

2012, Vol.24(4): 111–114 Abstract ( 516 ) PDF (340 KB) ( 410 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.022

The deep heavy oil reservoirs in the Tuyuke Oilfield are characterized by complicated structure, poor physical properties and low single well production, so it is difficult to achieve economical and effective development by using conventional mining methods and well-bore technology. The natural gas dissolution and viscosity reducing indoor experiments were tested on the deep heavy oil reservoirs in the Tuyuke Oilfield. The parameters of the design throughput were optimized by the use of numerical simulation and phase equilibrium studies in CEMway of exploitation on natural gas throughput. The gas throughput field tests were carried out on three wells. The results show that with the using of natural gas throughput technology, the daily production of a single well was increased 2～7 times.

Study on fracturing potential of water driving oil wells in extra-high water cut stage

ZHANG Wen， WANG Luchun， GUO Weiqi， ZHAO Xin

2012, Vol.24(4): 115–120 Abstract ( 466 ) PDF (364 KB) ( 514 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.023

Along with the oilfield entering into extra high water cut stage，the fracturing objects of water driving oil wells are becoming poor，and also the selection of fracturing wells and layers is more and more difficult. Based on reservoir engineering and real oilfield situation，we selected and analyzed the main influencing factors of fracturing effects by using multiple correlation and grey association methods, including effective thickness of the fracturing layers，permeability of the fracturing layers，ratio of formation coefficient of the fracturing layers to formation coefficient of the whole well，water cut of the whole oil well before fracturing， fluid quantity per day of the whole oil well before fracturing and pressure difference before fracturing. We used the group method of data handling （GMDH）to establish the regression model between the fracturing oil production enhancement and the main influencing factors, used the input-output principle of economics to establish the economic limit model of fracturing oil production enhancement，and defined that whether the fracturing oil production enhancement is economic or not is related to fracturing inputs and corresponding change of cost.

A steady seepage flow model of horizontal wells based on fluid compressibility and stress sensitivity

ZHANG Qiang， LIU Shengguo， ZHANG Junsong， WANG Jian， FENG Jingsha

2012, Vol.24(4): 121–124 Abstract ( 578 ) PDF (491 KB) ( 448 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.024

The seepage field of horizontal wells can be divided into outer region, which is a radial flow to an ellipse vertical well, and inner one, which is an ellipsoid flow to horizontal well. Each seepage model is deduced considering fluid compressibility and stress sensitivity, and then the formula for the performance of horizontal well is gained by utilizing conformal transformation and equivalent flow resistance law. Compared with classic formula, the derived formula is reasonable and reliable. When considering fluid compressibility and stress sensitivity, it means when α is not equal to zero, there is no longer a linear relationship between conduction of horizontal well and the drawdown pressure; the production will decrease with the increasing of CK and increase with the increasing of Cρ . When stress sensitivity is strong, it increases slowly with the increasing of drawdown pressure.

Influence of non-liner flow on productivity of abnormal high pressure gas reservoir

WANG Xiaoqin， WU Ju， RAN Yan， JIA Sha， ZHANG Nan

2012, Vol.24(4): 125–128 Abstract ( 605 ) PDF (359 KB) ( 525 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.04.025

The development of abnormal high pressure and lowpermeability gas reservoirs is not only affected by stress sensitivity but also influenced by start-up pressure gradient. In view of the particular flow characteristics of this kind of gas reservoir, three flow differential equations are derived which take stress sensitivity, start-up pressure gradient and both of them into account. Furthermore, taking an abnormal high pressure and low permeability gas reservoir as an example, we studied the effects of stress sensitivity and start-up pressure gradient on the productivity. The results show that stress sensitivity and start-up pressure gradient have a great impact on the development of abnormal high pressure and lowpermeability gas reservoirs, and the flow differential equations for this kind of reservoir considering stress sensitivity, start-up pressure gradient and both of the two, have some guidance for the study on flowcharacteristics of this kind of reservoir.