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01 January 2019, Volume 35 Issue 2 Previous Issue    Next Issue

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The Tight Oil Accumulation Model and Geological Characteristics in Continental Sedimentary Basins of China YAN Weipeng, YANG Tao, MA Hong, GUO Bincheng, HUANG Fuxi, TANG Hui 2014, 35 (2):  1-1.  Abstract ( 135 )   PDF (300KB) ( 239 )   Save The exploration practices in recent years confirmed that tight oil is widely distributed in continental sedimentary basins of China. Some significant discoveries have been obtained in Ordos basin, Junggar basin and Songliao basin, etc. At present the cognition degree about tight oils in China is still relatively low. This paper divided tight oil into four accumulation models, three matching relationships of source and reservoir and two reservoir types of sandstone and carbonate rock, according to the lake?level fluctuation and sediment supply, saline lacustrine basin depositional feature, development and disposition relationship of source rock and reservoir as well as tight reservoir lithology, etc. Also, this paper analyzed the geological characteristics of scale and physical properties of tight reservoirs, and discussed their significances for petroleum exploration for the purpose of providing references for China’s continental tight oil exploration Related Articles | Metrics

New Understandings of Natural Gas Accumulation and Distribution with Prediction of Favorable Exploration Plays in China LI Jun1,2, WU Xiaodong1, YANG Baisong3, YANG Shen2, LIU Yan4, LIN Shiguo2 2014, 35 (2):  1-1.  Abstract ( 86 )   PDF (300KB) ( 330 )   Save The in?depth research in this paper indicates that the accumulation and distribution of natural gas is characterized by cylicity, sequentiality, balance, traceability and multiphase, namely each tectonic sedimentary cycle signifies one gas accumulation system; in each system the generation, migration, accumulation of natural gas are characterized by a certain series; the significant factor for gas accumulation is the balance between migration force and resistance; the closer the distance from hydrocarbon source rocks, the higher the gas accumulation efficiency is, so the multiphase accumulation of gas is its feature in the long geological history. A large gas field is generally controlled by five features in its forming and distribution. The inner hydrocarbon source rocks and adjacent to the source rock area, unconformity zones and faulted anticlinal belts are favorable areas for large gas fields distribution. In addition to unconformity zones and faulted anticlinal belts that have been found more like these nowadays, the inner source area and proximal realm should be the domains for petroleum exploration in the future. The Carboniferous-Permian in southeastern Ordos basin, the Triassic in southwestern Sichuan basin and the Jurassic in Kuqa depression of Tarim basin which haven’t got a major breakthrough could be the significant plays for next exploration of petroleum Related Articles | Metrics

The Formation Mechanism of Abnormal High Pressure Reservoirs in Dongpu Sag, Bohai Bay Basin XUE Guogang1, GAO Jianzhen2 2014, 35 (2):  1-1.  Abstract ( 81 )   PDF (300KB) ( 200 )   Save The study of the distribution characteristics of abnormal high pressure reservoirs in Dongpu sag in Bohai Bay basin shows that the measured abnormal high pressure in this sag can be divided into source rock abnormal high pressure and reservoir abnormal high pressure. The main reason of the former is the late hydrocarbon generation, and that of the latter includes effective plugging effect caused by salt or shale, its oil and gas saturation and maturity. The secondary hydrocarbon generation served as the material basis for its late hydrocarbon accumulation in condition of deep abnormal high pressure. Such a reservoir is characterized by late formation time, short oil?gas migration distance, high gas?oil ratio and big reservoir pressure factor, etc., and generally distributed in slope zone and sides of an uplift belt, with buried depth of less than 4 300 m Related Articles | Metrics

The Characteristics of Sedimentary Provenance and Facies of Second Member of Xiazijie Formation in Bai21 Well Block, Junggar Basin ZHANG Youping 2014, 35 (2):  1-1.  Abstract ( 60 )   PDF (300KB) ( 230 )   Save Based on the characteristics of heavy mineral combination, seismic facies, wave impedance inversion, the single well and multiwell facies section as well as the high?resolution sequence stratigraphy, the sedimentary provenance and sedimentary facies of the second member of Xiazijie formation in Bai?21 well block in Junggar basin are analyzed. The result shows that the Xiazijie formation developed an alluvial fan and the sedimentary provenance is in direction of north to slight west; the second member of the Xiazijie formation developed five sedimentary cycles, the lower two cycles are dominated by braided stream channel deposit and the upper three by lateral margin of braided stream zone and over bank sand, reflecting the reducing process of the fan sedimentary scope Related Articles | Metrics

The Mechanism of Occurrence State of Shale Gas ZUO Luo1,2,3, XIONG Wei1,2, GUO Wei1,2,3, GAO Shusheng1,2, HU Zhiming1,2 2014, 35 (2):  1-1.  Abstract ( 82 )   PDF (300KB) ( 383 )   Save The forces and the occurrence states of shale gas in various pore types are analyzed by different types and sizes of pores and by means of Lee potential?energy function. It is suggested that shale pores can mainly be divided into three types: organic pore, clay mineral pore and nonclay mineral pore, and each pore has its typical feature; the methane molecules in each pore are effected by dispersion force, some methane molecules near the pore walls are adsorbed by dispersion force, some are in free state when they are not effected by the force; with the increase of shale pore sizes, the proportion of area affected by pore wall is decreased and the adsorption ability of pores goes down; the adsorbed gas is mainly distributed in the pores less than 10 nm, the adsorption abilities of the organic matter and the clays with lots of micropores are higher than other minerals; in organic and clay pores, the shale gas exists by way of adsorbed gas and free gas, while in mineral pore, it does by free gas Related Articles | Metrics

Hydrocarbon Accumulation Conditions and Types of Nantun Lithologic Reservoirs in Tanan Sag LI Yanjie, ZHANG Yajin 2014, 35 (2):  1-1.  Abstract ( 56 )   PDF (300KB) ( 245 )   Save Tanan sag is located in the south of Tamtsag basin. Its lithologic reservoirs are one of major realms for petroleum exploration in this area as the most realistic reservoir type for increase of reserves. This paper studies the inherent regularity of lithologic reservoirs and confirms the type of Nantun lithologic reservoir, combined with integrated structural reservoir exploration research. After in?depth analysisof the reservoir?forming conditions, it is shows that the source rocks of Nantun formation in Tanan sag are characterized by high abundance of organic matter, development of fan delta and delta sedimentary system as well as reservoir facies belts. The development of delta front, nearshore subaqueous fan?in?fan and offshore subaqueous fan facies provides effective reservoir spaces for lithologic reservoir; the multiple conducting types include fault, pore, fracture and sand body; the good conservative conditions allowed to form two sets of regional caprocks of Nantun formation and Damoguaihe formation. In this study area three types of lithologic oil and gas reservoirs are distributed: updip pinchout sandstone reservoir, sand lens reservoir and fault lithologic reservoir Related Articles | Metrics

The Qiketai Tight Oil Reservoir Characteristics of Jurassic in Tuha Basin ZHU Youxin, LI Xinning, PU Zhenshan, ZHAO Hao, MA Qiang, SONG Xueliang 2014, 35 (2):  1-1.  Abstract ( 72 )   PDF (300KB) ( 221 )   Save The systematic researches of the geological conditions of tight oil of Qiketai formation of Jurassic in Turpan?Hami (Tuha) basin and its prediction of favorable areas are made in this paper based on data from a lot of source rocks and reservoir tests, compared with related well logging and seismic imformation. The results show that the tight oil reservoir is mainly distributed in the upper section of Qiketai formation and Taibei sag, with thickness of 30~130 m. The lithology is dominated by gray dolomite, dark mudstone and marl, widely developing structural fractures, intergranular pores and dissolved micropores, and the average content of quartz + carbonate +feldspar is over 65%. The underlying hemi?deep lake facies mudstone is regionally stable in distribution, largely contacting with the overlying reservoirs. Through superimposition of the superior hydrocarbon and the tight reservoir, this paper predicts the favorable area for tight oil exploration, with sweet spot area of 550 km2, mainly distributing around Shengbei 11- Shengbei 10-Liansha 2 well area Related Articles | Metrics

The Forming Mechanism of Fluid Compartment in MiddleShallow Reservoirs in Nanyishan Oilfield, Qaidam Basin YU Tingxu1, ZHANG Junfeng2, WANG Liqun3, XUE Jianqin3, XU Hao1, WANG Kai3 2014, 35 (2):  1-1.  Abstract ( 63 )   PDF (300KB) ( 239 )   Save The middle?shallow reservoir of Nanyishan oilfield in Qaidam basin is characterized by the coexistence of abnormal low pressure, normal pressure and weak abnormal overpressure. Aiming at the characteristics, this paper presents the constitutive model and feature for the fluid pressure compartment of such a reservoir in this area. The study shows good reservoir sealing ability in the reservoir, which is also reflected by its light crude oil, low viscosity, saturated hydrocarbon value of m(ΣnC21-)/m(ΣnC22+). It is suggested from the multi?well section with predicted and measured pressure coefficients that the abnormal low pressure and normal pressure?weak abnormal overpressure fluid compartment is characterized by vertical superimposition and along?bedding distribution, where local abnormal overpressure belt occurs near the faults due to differential fluid charging in the abnormal low pressure compartment. The constitutive model for the compartment is as follows: the bottom is the Upper Ganchaigou source rocks with capillary pressure and abnormal pressure dual sealing mechanism; the top is the Upper Youshashan formation with saline sediments of shale and marl interbedded with gypsum layers; while the edge is shaped by the gradual changes into such a compartment from thrust fault interface with lateral sealing, rock facies and reservoir physical properties Related Articles | Metrics

The Organic Geochemistry of Palaeogene Oil Sands in Western Qaidam Basin LI Mengyao1, ZHAO Xin1, ZHOU Ke1, WANG Youxiao2 2014, 35 (2):  1-1.  Abstract ( 60 )   PDF (300KB) ( 198 )   Save Based on the extraction and the GC?MS analysis of saturated hydrocarbons from oil sand samples of the Palaeogene Lower Youshashan formation and Lower Ganchaigou formation in western Qaidam basin, the geochemical characteristic of biomarkers in these hydrocarbons are studied. The results show that the hydrocarbons of oil sands and crude oils formed in a strong reducing saline lacustrine depositional environment. The type of organic matter is mainlyⅡkerogen, in which contains abundant C27 regular sterane, hopance and long?chain tricyclene, reflecting the contribution of the algae of lower aquatic plants and bacteria to the hydrocarbons from organic matter. The ratios of m(ααα C29 sterane 20S)/m[αααC29 sterane (20S+20R)] and m(ααα C29 steraneββ)/m[ααα C29 sterane (αα+ββ) ] reveal that the oil sands of Lower Youshashan and Lower Ganchaigou formations are generated after low mature? mature crude oil migrating into the reservoir. The loss of relative low n?alkane and Pr and Ph suggests that hydrocarbons in the oil sands once endured heavy biodegradation and some other secondary alterations. It is related to the geological background that the oil sands were uplifted and exposed to the surface due to tectonic movement Related Articles | Metrics

10. New Understanding of Reservoir of Z2 Sand Layer of Ziniquanzi Formation in Hutubi Gas Storage LI Yifeng1a, LI Yonghui2, GAO Qi1a, WANG Bin1a, LI Daoqing1a, PANG Jing1a, LI Wenjing1b 2014, 35 (2):  1-1.  Abstract ( 93 )   PDF (300KB) ( 326 )   Save In order to guarantee the stable gas supply in the north Xinjiang and the West?East natural gas transmission project’s secondline strategy security, PetroChina Xinjiang Oilfield Company selected Hutubi gas field to rebuild underground gas storage. Based on the new drilling and coring data as well as well logs, this paper analyzes the reservoir properties such as rock mineral composition and petrophysical property variation, and the reservoir is divided into 4 types: high quality reservoir, secondary reservoir, poor reservoir and poornon reservoir. The E1-2z1-1 2 reservoir belongs to the secondary reservoir through in?depth understanding of the gas storage, which provides a basis for the underground gas storage steady running and gradual expansion in the future Related Articles | Metrics

Establishment and Application of Generalized Tong’s Chart CHEN Yuanqian, GUO Erpeng 2014, 35 (2):  1-1.  Abstract ( 89 )   PDF (300KB) ( 432 )   Save In 1978, Academician Tong Xianzhang proposed the chart method for determination of water drive recoverable reserves based on Type A water drive curve. This chart was cited by the national standards of petroleum industry published in 1989, 1998 and 2010 in China. For the chart is intuitive, simple and applicable, it is very popular and highly regarded by all reservoir engineers. However, it was restricted in application and resulted in uncertainties because the chart was made based on water cut limit of 98%. In this paper, the generalized Tong’s chart is established based on Tong’s work. The generalized chart can not only expand in application range, but also improve reliability for forecasting recovery efficiency. Using the matching water cut with Tong’s chart, the recovery factor and the recoverable reserves can be determined. The field application shows the generalized chart is effective and practical Related Articles | Metrics

Transient Pressure Behavior Analysis and Direct Synthesis Technique for Horizontal Well Intersected by Finite Conductivity Fractures WANG Junlei1 , WEI Yunsheng1 , CHEN Peng2a , HAN Huiping2a , HUANG Yougen2b,2c 2014, 35 (2):  1-1.  Abstract ( 65 )   PDF (300KB) ( 229 )   Save In the model of horizontal well intersected by finite conductivity fractures (HWFCF), a dynamic factor was derived to simulate the characteristic of flowing in fracture. Pressure superposition principle was incorporated to deal with the interaction of fractures in Laplace transform. Production rates from fractures and wellbore pressure constituted the system of linear equations which could be solved by utilizing stehfest numerical inversion and numerical iteration method. The result shows that the whole flow duration can be divided into five segments: bilinear flow, linear flow, radial flow, compound linear flow and compound radial flow. Meanwhile, the approximate expressions of pressure and derivative in different segments were presented based on the equivalent wellbore radius and asymptotic approximation. Applying the principle of Tiab’s direct synthesis technique to the case of HWFCF, formation permeability, facture length, finite conductivity,distance and skin factors were calculated without using the type curve matching procedure or regression Related Articles | Metrics

Benchmarking and Its Enlightenment for LG7 Pilot Test Area in Lungu Oilfield, Tarim Basin REN Kangxu, SONG Xinmin, ZHANG Hansong, WANG Jue, DU Yijing, WANG Xingmeng 2014, 35 (2):  1-1.  Abstract ( 67 )   PDF (300KB) ( 167 )   Save Related Articles | Metrics

Identification and Control Technologies for Thick Heavy Oil Reservoirs by InSitu Combustion Drive Process JIANG Qin, JIN Zhaoxun 2014, 35 (2):  1-1.  Abstract ( 69 )   PDF (300KB) ( 451 )   Save Gao?3618 block in Liaohe oilfield is a typical thick glutenite heavy oil reservoir. It has been carried out combustion drive pilot test and extended to 13 well groups in view of a large number of remaining oil between wells on the last phase of the steam stimulation development in May 2008. By the field studies and practices such five key supporting technologies were preliminarily formed as ignition, communication status evaluation, combustion condition evaluation, combustion front driving evaluation and response feature evaluation. Through the application to Gao?3618 block, its combustion drive effectiveness has been gradually improved, basically reaching the expectations of“ignition success, general effect, high temperature combustion and uniform driving” Related Articles | Metrics

Stimulation Mechanism of Acid Fracturing in Fractured Tight Sandstone Reservoirs ZHAO Shunchao1, LUO Zhifeng1, YUAN Xuefang2, ZHAO Liqiang1, YE Jing1 2014, 35 (2):  1-1.  Abstract ( 69 )   PDF (300KB) ( 224 )   Save Hydraulic fracturing and matrix acidizing as the stimulation measures for fractured tight sandstone reservoir have their limitations. Acid fracturing technology applied to the target reservoir has obtained the remarkable effect to increase production. For specific reservoir, this paper calculated the shear?slip conditions occurred in natural fractures and simulated the effect of acid fracturing liquid on calcite?infilling fracture and shear?slip fracture by experiment. The study shows that compared with the conventional stimulation operations, acid fracturing mainly relies on the following two effects to obtain high flow conductivity: shear?slip occurs in natural fracture under the action of hydraulic stress, and the surface roughness of fractures can form the self?supporting; acid liquid corrodes the fillings, harmful substances and part of rock matrix to increase residual unclosed fracture space, hence improving the fracture conductivity. On the basis of mechanism study, this paper puts forward implementation suggestion of the process Related Articles | Metrics

Efficiency of Oil Displacement by UltraLow Concentration Organic Chromium CrossLinked Polymer Gel LI Sen1, CHENG Zhiqiang2, LI Ronghua2, QIAO Qi2, WEI Xiuping2 2014, 35 (2):  1-1.  Abstract ( 58 )   PDF (300KB) ( 240 )   Save By physical simulation parallel core displacement test, the range of EOR by gel system will obviously decline with the increase of polymer concentration in the conditions of core permeability ratio of 60 times, polymer concentration of 200~800 mg/L and total chromium cross?linked polymer gel injection of 0.2 PV. The result shows that the ultra?low concentration polymer organic chromium gel system has high viscosity and stability after injecting into the reservoir, avoiding the affect of many uncertain factors caused by the polymer gel injecting into the reservoir on the gel system. It is concluded that the duel?tube parallel core displacement test can improve EOR by 9%~16% Related Articles | Metrics

Analytical Calculation Model for Coalbed Methane Compressibility Factor SUN Hongming1, FU Xuehai1,2, DING Yongming3, LIANG Yuelin4 2014, 35 (2):  1-1.  Abstract ( 71 )   PDF (300KB) ( 421 )   Save Coalbed methane compressibility factor is necessary to calculate the free gas in coal reservoir. The data of coalbed methane compressibility factor is usually obtained by checking methane compression factor table, however, this method is not so accurate. In order to establish an analytical calculation model for coalbed methane compressibility factor, which is suitable for conditions of the composition of coalbed methane and the temperature and pressure of coal reservoir, REFPROP 8.0 sofware is used to calculate the methane compressibility factor at temperature of 0~100℃ and pressure of 0~30 MPa. An analytical calculation model for pure methane compressibility factor is established with reduced temperature and reduced pressure as independent variables. Based on this model, an analytical calculation model for coalbed methane compressibility factor is established by means of corresponding states principle and weighted processing approach. The calculated result from this model shows that the relative error is less than 2.5%, with an average value of 1.48%. This model can be used to calculate free gas content in coal reservoir Related Articles | Metrics

Using Strontium Isotope Ratio for Evaluation of Reservoir Connectivity in Rumaila Oilfield, Iraq ZHOU Jiasheng1, TIAN Changbing1, ZHANG Weimin1, WANG Zhao2 2014, 35 (2):  1-1.  Abstract ( 71 )   PDF (300KB) ( 291 )   Save Reservoir connectivity evaluation is vital for efficient development of oilfields, accurate understanding of reservoir connectivity will affect its reserves estimation, development strategy, and even decide the success or failure of oil and gas field development. The conventional methods for it include the sedimentary facies analysis, lithofacies analysis, formation pressure analysis and reservoir fluid compositional analysis. However, these methods have their uncertainties or limitations. In this paper, the strontium isotope residual salt analyses (SrRSA) methodology is introduced. This information from the cored well in Rumaila oilfield in Iraq are applied to analyzing the reservoir vertical and lateral connections, thus demonstrating that in Main Pay sandstone reservoir formation occurs the vertical disconnection. So this reservoir is divided into three sets of development sequences; the major Mishrif carbonate reservoir is good in lateral connectivity, its oil?water interface is controlled by structure; the potential Yamama reservoir is poor in lateral connectivity, and its oil?water relationship is complicated, the fluid distribution is controlled by lithology. The case study indicates that the SrRSA information is one of the most efficient and economical methods for deterministic evaluation of reservoir connectivity, and it is of great significance for references and widely application Related Articles | Metrics

Seismic Data Spatial Sampling and Energy Joint Regularization: Method and Application ZHANG Tao, WANG Yuchao, TIAN Yancan, LU Lieqin 2014, 35 (2):  1-1.  Abstract ( 45 )   PDF (300KB) ( 290 )   Save This paper studies the influencing factors of seismic data on prestack imaging quality and suggests that the prestack data regularization should be performed by both homogenization processing of data spatial sampling and data energy. By means of borrowing nearest traces, the normalization of data spatial sampling can improve the signal to noise ratio of migration imaging; using triangulation method for normalization of data amplitude energy may decrease the migration noise and strengthen AVO attribute. By joint regularization processing of prestack seismic data and application to Nanpu area, the imaging quality after regularization is much more improved than that before it, including improvement of signal to noise ratio in shallow and suppression of noise in deep zone as well as amplitude preservation Related Articles | Metrics

Phased Fracturing Technology and Field Applications for Open Hole Horizontal Wells LU Yanjun1, YANG Zhaozhong1, LI Xiaogang1, HUANG Junping2, ZHANG Shide2 2014, 35 (2):  1-1.  Abstract ( 82 )   PDF (300KB) ( 361 )   Save The operation process simplicity and high operating efficiency allow the phased fracturing technology for open hole horizontal wells to be widely used in the stimulation of low?porosity, low?permeability and low?pressure reservoirs. The key of it is the open hole completion tools of which packer and sleeve are the important part. On the basis of previous studies, the structures and working principles of he well completion tools are analyzed, the open hole induced fracture initiation model for the horizontal wells is developed, and the formula about the fracture initiation model is derived. Combining with formulas of string friction, perforation friction and hydrostatic pressure, the heoretically calculated breakdown pressure is consistent with that in the fracturing operation curve. Finally, the main factors of influencing sleeve open are analyzed by the calculated staged fracturing fracture?initiation pressure Related Articles | Metrics

New Classification Scheme of Limestones JIN ZhenkuiShao Guanming 2014, 35 (2):  1-1.  Abstract ( 107 )   PDF (300KB) ( 1068 )   Save Classification of limestones is the foundation for study of limestone origin and sedimentary facies. Because of the existence of various problems in previous classification schemes of limestones, no classification scheme of limestones is widely accepted at present in China. So different scholars adopt different classification schemes, resulting in chaos in naming and classification of limestones, such as different names for one limestone, or different implications for one name. On the basis of analysis of previous classification schemes, this paper proposes a new classification scheme of limestones. Based on the types and content of textural components, limestones are divided into limemudstone, grain?bearing limemudstone, grainy limemudstone, grainstone (including limemud grainstone and sparry grainstone), reef limestone (including limemud reef limestone and sparry reef limestone), reef clast limestone (including sparry reefclast limestone and limemud reefclast limestone). Each type can be divided further based on grain type and reef?building organism type or based on mineral components by Class?3 nomenclature Related Articles | Metrics

Tight Oil Accumulation Characteristics and Selection Criteria for Potential Basins MA Feng1, WANG Hongjun1, ZHANG Guangya1, HE Zhengjun1, YANG Liuyan1, LI Fei2 2014, 35 (2):  1-1.  Abstract ( 87 )   PDF (300KB) ( 538 )   Save Based on statistic and compared all available definitions of tight oil given by oil exploration scholars across the world, it can be defined that tight oil, which can be economically recovered only by large fracturing, is continuously accumulated within the source rock as well as its top and bottom, with tight clastic rock and carbonate rock as the reservoir rock, permeability less than 1 mD and porosity less than 12%. According to 8 parameters summarized after successful exploration and development of mature shale blocks in North America,the tight oil is of 10 accumulation characteristics: (a) special shale type is required; (b) organic matter abundance reaches a given level; (c) organic matter thermal maturity lies in the oil window; (d) organic matter type is mainly Type I and Type II; (e) organic?rich shale thickness reaches a given scale; (f) interbeds with good porosity and permeability exist between shale rocks; (g) overpressure conditions exist; (h) shale has high Young’s modulus and low Poisson’s ratio; (i) brittle minerals content is high; (j) crude oil is light. On these bases, this paper points out the differences between tight oil and shale gas in source rock quality and reservoir characteristics for economic development, and presents the assessment criteria for potential shale in tight oil basins from analyzing the geological conditions of tight oil accumulation in North America: TOC>2%, Ro: 0.5%~1.3%, ρr<0.87 g/cm3, μo<10 mPa·s. According to this criteria, 98 basins with tight oil exploration potential have been screened out across the world, their tight oils are mainly distributed in Mesozoic and Paleozoic Related Articles | Metrics