Table of Content

01 January 2017, Volume 37 Issue zk(English) Previous Issue    Next Issue

For Selected:

Download Citations EndNote Reference Manager ProCite BibTeX RefWorks

Toggle Thumbnails

OIL AND GAS EXPLORATION

Optimization of Favorable Reservoir-Caprock Assemblages of Middle-Upper Permian in Mahu Sag, Junggar Basin YANG Fan, WEI Yanzhao, Abulimiti, CHEN Gangqiang, BIAN Baoli 2016, 37 (zk(English) ):  1-7.  Abstract ( 59 )   PDF (7230KB) ( 24 )   Save This paper presents the sequence stratigraphic classification of single well of the Middle-Upper Permian in slope area surrounding Mahu sag of Junggar basin, and the sequence stratigraphic correlation of well logging and seismic profile, dividing the Xiazijie formation, the lower Wuerhe formationtion and the upper Wuerhe formation into two second-order sequences and six third-order sequences, and recognizes the thick glutenite reservoirs of the middle-lower part of Xiazijie formation, the lower and upper parts of lower Wuerhe formationtion, and upper Wuerhe formation, as well as three regional caprocks in the upper part of Xiazijie formation, the middle part of lower Wuerhe formationtion and the top of upper Wuerhe formation, by which three favorable reservoir-caprock assemblages are given. The middle and lower assemblages are controlled by low stand system tract’s slope break belt, and dominated by lithologic and structural-lithologic reservoirs;; the upper one is controlled by large-scale unconformities of the Permian-Triassic and the lower Wuerhe formationtion-upper Wuerhe formation, and dominated by stratigraphic reservoir which is characterized by relatively shallow burial, matching well with oil source faults and high efficient petroleum transport system, it could be an important area for the recent hydrocarbon exploration. References | Related Articles | Metrics

Geochemical Characteristics of Aromatic Hydrocarbons in Crude Oil of Shawan Formation in Chunguang Block, Northwestern Margin of Junggar Basin YIN Qin, YAN Yongxin, WANG Yong, JIA Xiurong, JI Tiantian, MA Rongfang 2016, 37 (zk(English) ):  8-13.  Abstract ( 53 )   PDF (1931KB) ( 147 )   Save In order to ascertain the oil-gas origin in Chepaizi area in northwestern margin of Junggar Basin, this paper studies the 40 crude oil samples from the Miocene Shawan formation in Chunguang block of the basin using GC-MS analysis, and presents the distributions and compositions of aromatic hydrocarbons biomarker, as well as their geological and geochemical implications. There are abundant aromatic hydrocarbons detected in Shawan crude oil, which can be regarded as an important basis for the judgement of organic matter maturity, kerogen type, hydrocarbon charge and migration direction. The study shows that the Shawan crude oil is in mature stage, formed in continental oil environment, and its kerogen contains a certain extent of input higher plants, and there exist some differences among precursors for different types of crude oils. According to the RPN and m(4-MDBT)/m(1-MDBT), the Shawan crude oil in this area is originated from WS to ES directions, and characterized by that the light crude is close to hydrocarbon source area, with single oil source; the intermediate and heavy oils are relatively far from it, the former is mixed oil, the latter is highly degraded one. References | Related Articles | Metrics

Abnormal High Pressure and Tight Oil Enrichment of Lucaogou Formation in Jimusar Sag LIAN Huan, ZHA Ming, GAO Changhai, TANG Yong, DING Xiujian, QU Jiangxiu 2016, 37 (zk(English) ):  14-19.  Abstract ( 54 )   PDF (2111KB) ( 129 )   Save The tight oil reservoir of the Middle Permian Lucaogou formation in the Jimusar sag is of good hydrocarbon potential. Its enrichment mechanism is greatly different from that of conventional oil-gas reservoirs. This paper calculates the fluid pressure of this formation, establishes the abnormal high pressure distribution system of it, and combined with the geologic conditions, geochemical analysis and formation testing of key wells, it discusses the relationship between the abnormal high pressure and tight oil enrichment. The results show that the Lucaogou reservoir is of typical integrated source-reservoir structure, and the tight oil generated from high-quality source rocks in low mature-mature stages is characterized by self-generation and self-storage, or migrated in short distance between source rocks, which is the main reason for forming the abnormal high pressure. Such abnormal high pressure is widespread in the source rocks and the reservoirs, with lateral stability and connectivity, showing a certain “strata bound” characteristic;; with vertical differences in organic matter abundance and hydrocarbon generation ability in different strata, resulting in uneven distribution of the abnormal high pressure, indicating that there exists distinct interlayer remaining fluid pressure. Such a remaining fluid pressure could be the main force for vertical migration of the tight oil, and the distribution belts of big difference of the interlayer remaining fluid pressure might be the favorable area for tight oil enrichment. References | Related Articles | Metrics

Structure and Geological Significance of Pishan Caldera in Tarim Basin ZHANG Changjian, LIU Shaojie, LUO Shaohui, WANG Ming 2016, 37 (zk(English) ):  20-24.  Abstract ( 69 )   PDF (4495KB) ( 211 )   Save On the basis of caldera theory integrated with seismic-lithofacies interpretation and tectonic evolution, the paper investigates the structures of Pishan caldera and describes its impact on the Cretaceous reservoirs. It is considered that the large-scaled composite caldera in Pishan formed in the late Hercynian movement, which is a circle with the diameter of 25 km and the maximum subsidence depth of 1.5 km. Volcanic materials erupted in central and fissure mode along the circular fault and the evacuation of magma chamber resulted in sharply subsidence. Volcanic eruption facies, lacustrine facies and Cretaceous breccia facies assume the circular symmetric distribution; inner-dipping circular normal faults and outer-dipping circular inverse faults are developed in collapse structure area and high-steep divergent inverse faults occur in central dome structure area, which indicates the complete process of caldera from its first eruption, subsidence to re-activation.Pishan caldera structure controls the development and distribution of the Cretaceous reservoirs. References | Related Articles | Metrics

Simulation Experiment Study on Dynamic Hydrocarbon Accumulation of Fault-Block Sandstone Reservoirs WU Ping 2016, 37 (zk(English) ):  25-28.  Abstract ( 66 )   PDF (783KB) ( 164 )   Save In order to study dynamic hydrocarbon accumulation in fault-block sandstone reservoirs, related simulation experiments are carried out on the differences of filtration capacities between oil and water and the impact of hydrodynamic conditions on oil enrichment during the dynamic oil accumulation. The result shows that significant difference exists in oil and water filtration capacities, oil filtration capacity is lower than that of water, which results in the oil accumulation in cores and then the dynamic oil enrichment in permeable media; oil enrichment is constrained by hydrodynamic conditions during hydrocarbon charging, and the stronger the hydrodynamic force is, the easier the oil enrichment will be, and the higher the enrichment degree will be, too. It is assumed that appropriate-open reservoirs sheltered by normal faults are in accordance with the dynamic reservoir accumulation patterns and the application of the dynamic model could macroscopically explain the relationships among the effectiveness of fault sheltering, complicated physical property distribution of fault block reservoirs, accumulation of fault-sheltered reservoirs and hydrocarbon generation setting in the basin and so on. References | Related Articles | Metrics

Discovery and Hydrocarbon Accumulation Mechanism of Quasi-Continuous High-Efficiency Reservoirs of Baikouquan Formation in Mahu Sag, Junggar Basin ZHI Dongming 2016, 37 (zk(English) ):  29-39.  Abstract ( 78 )   PDF (5826KB) ( 315 )   Save In recent five years, great breakthroughs have been made successively in the Lower Triassic Baikouquan formation in hydrocarbon-rich Mahu sag in the northwestern margin of Junggar basin, and the above-source quasi-continuous reservoirs with the reserves over hundreds of millions of tons are firstly discovered, which should be attributed to the changes of thoughtway from structural reservoir exploration to lithologic-stratigraphic reservoir and continuous reservoir exploration. Composite analysis on hydrocarbon accumulation mechanism shows that high-quality Carboniferous-Permian source rocks are developed in hydrocarbon-rich Mahu sag, which is favorable for oil generation; high-quality reservoirs and structural-lithololgic traps of fan-delta front facies are developed in Baikouquan formation, in which faults connect the source rock and the reservoir, which helps hydrocarbon accumulation; gentle structures with good top and bottom conditions in Baikouquan formation are in favor of hydrocarbon enrichment; abnormally high pressure and fractures occur in Baikouquan formation, and the oil here is of good quality and reservoir sweet spots are developed, which is good for high oil production. Therefore, quasi-continuous reservoirs with the reserves of hundreds of millions of tons in Baikouquan formation in Mahu sag are characterized by extensive oil distribution, local oil enrichment, jointly controlled by nose-like structural belts and favorable belts in delta front as well as faults, high-efficiency accumulation and great prospecting potential, which can be an important supplement to continuous reservoir exploration and research in the world. It is suggested that Huangyangquan fan, Mahu E fan and Xiayan fan with relatively low exploration degree should be focused on for further petroleum exploration at present. References | Related Articles | Metrics

Genetic Mechanism of Intragranular Fractures in Low-Permeability Sandy Conglomerate Reservoir and Their Significance in Petroleum Exploration: A Case Study from Triassic Baikouquan Formation in Mahu Sag, Junggar Basin XU Yang, MENG Xiangchao, LIU Zhanguo, SHAN Xiang 2016, 37 (zk(English) ):  40-48.  Abstract ( 66 )   PDF (5463KB) ( 165 )   Save The sandy conglomerate reservoirs of Baikouquan formation of Mahu sag in northwestern margin of Junggar basin are low-porosity and low-permeability reservoirs, where the intragranular fractures act as the important flow paths. Less researches have been made in terms of genetic mechanism and development of intragranular fractures at home and abroad. This paper systematically analyzes the identifying characteristics, genetic mechanism, development process and distribution of intragranular fractures in low-porosity and low-permeability sandy conglomerate reservoirs, according to the macroscopic and microscopic characteristics of intragranular fractures development, combining with drilling and seismic data, by means of relationship characterization of the palaeotectonic stress value-the intragranular fractures, and intragranular fracture physical modeling experiment. It is considered that the intragranular fractures in Baikouquan formation are structural-diagenetic fractures genetically, the generation of the fractures is related to the properties of compression, shearing and torsion, internal defect of grains, tectonic stress and stress effect; the main influence of intragranular fractures on the reservoir is to improve reservoir permeability, and the effective configuration of intragranular fractures in coarse grains-intergranular matrix pores among sand grains-microfissures is the key factor to generate high-quality and high-efficiency reservoirs of Baikouquan formation; the intragranular fractures are mainly distributed in Middle-Lower Triassic Baikouquan formation vertically and mostly in Wuerhe-Xiazijie faulted belt in plane. The development degrees of intragranular fractures in Karamay-Baikouquan and Wuerhe-Xiazijie faulted belts are different due to the changes of stress effect mode and rigid grain content. Constrained by thrust fault distribution, the development degree of intragranular fractures is weakening from the faulted zone to slope area, but tends to increase at strike-slip faults. References | Related Articles | Metrics

Controls of Tectonic Activity on Alluvial Fan Deposits and Hydrocarbon Accumulation: A Case Study of Permian and Triassic Alluvial Fans in Northwestern Margin of Junggar Basin YIN Senlin, TANG Yong, HU Zhangming, WU Tao, ZHANG Lei, ZHANG Jiyi 2016, 37 (zk(English) ):  49-59.  Abstract ( 67 )   PDF (5183KB) ( 170 )   Save The coupling relationship between tectonic activity and alluvial fan deposits is one of the hot spots and difficulties in tectono-sedimentology research. Uncommon and widespread glutenite bodies are developed along the fault zone in the northwestern margin of Junggar basin. Therefore, studies on the controls of tectonic activity on alluvial fans and hydrocarbon accumulation are of great theoretical and practical significance. Using the data of cores, logging and seismic profiles, this paper studies the distribution of structure-controlled alluvial-fan glutenite bodies, and the hydrocarbon accumulation patterns combined with related oil and gas accumulation data. It is shown that the superimposition pattern of alluvial fans is closely related to the activity of contemporaneous faults, and there are 3 typical distribution patterns of the fans under the control of contemporaneous faults, which include the retrograded alluvial fans against the source direction and controlled by normal comb-like fault combination, the laterally superimposed alluvial fans and vertically stacking alluvial fans controlled by reverse comb-like faults and crossing faults, and the progradational alluvial fans controlled by preceding faults. Tectonic activity has significant impact on provenance, landform and local climate during the formation of these alluvial fans. These factors jointly control the development and sedimentary sequence differences of alluvial-fan glutenite bodies at different positions of the structures. It is concluded that alluvial-fan glutenite reservoir forms under the effects of both structure and lithology, which is characterized by one reservoir in one fan, several reservoirs in one fan, and one reservoir in several fans. References | Related Articles | Metrics

Depositional Characteristics and Hydrocarbon Exploration Significance of Shallow-Water Deltas: A Case Study of Upper Sha-1 Member in Chaheji Structural Belt of Baxian Sag, Bohai Bay Basin LYU Chuanbing, CHENG Tongran, ZHANG Feng, JI Youliang, LIANG Guanzhong, LI Yanguo 2016, 37 (zk(English) ):  60-65.  Abstract ( 59 )   PDF (2001KB) ( 137 )   Save Reservoirs of shallow-water delta facies are the dominant oil and gas reservoirs in the upper Sha-1 member of Shahejie formation in Chaheji structural belt of Baxian sag in Jizhong depression, Bohai Bay basin. Based on the analyses of petrological features, tectono-sedimentary characteristics, grain sizes and fossils, the paper studies the sedimentary characteristics and sedimentary facies distribution of shallow-water delta systematically, summarizes the depositional model of shallow-water delta and describes the favorable accumulation conditions of shallow-water delta. The study results show that in the upper Sha-1 member, the distributary channel of shallow-water delta is well developed, river mouth bar does not occur and large-area sheet sands are extensively distributed. The cyclic variations of lake level result in sandstone interbedded with mud at multi-stages, which is the main controlling factor of sand body distribution. The sedimentary characteristics of shallow-water delta could determine that in this facies there exist pretty good reservoir-caprock assemblages and various traps are then formed due to faulting to sandbodies. The upper Sha-1 member in Chaheji structural belt has good oil and gas accumulation conditions. References | Related Articles | Metrics

Geochemical Characteristics of Crude Oil and Oil-Source Correlation in Halahatang Sag LI Zhongxuan, XU Zhiming, WANG Zhaoming, CHEN Yunchuan, XIAO Zhongyao 2016, 37 (zk(English) ):  66-72.  Abstract ( 64 )   PDF (1588KB) ( 119 )   Save The Halahatang sag in the Tarim basin is abundant in petroleum resources with the proved reserves over one hundred million tons. In order to confirm the major source rocks of Ordovician reservoirs in the Halahatang sag, systematic geochemical analyses are performed for oil samples from Well ZS1 and Halahatang sag and characteristics of light hydrocarbons and biomarkers are further studied. The results show that the Halahatang oil samples are characterized by high content of n-alkanes and poor content of arene, which are similar to those of oil samples from Well ZS1, indicating the typical sapropelic origin. The aryl isoprenoid compounds detected in the oil samples from the Halahatang sag are the markers for strong reducing sedimentary environment. Combined with the characteristics of source rocks and geological settings in the Halahatang sag, it is considered that the marine oil in the study area mainly originates from the Cambrian to Lower Ordovician source rocks instead of the Middle to Upper Ordovician source rocks. References | Related Articles | Metrics

RESERVOIR ENGINEERING

Analytical Method of Water Displacing Oil Theory GAO Wenjun, FU Yanxin, PAN Youjun, XU Yunheng, XU Ying, ZHANG Debin, WANG Shaoxia 2016, 37 (zk(English) ):  73-77.  Abstract ( 65 )   PDF (1207KB) ( 143 )   Save Based on the previous high-accurate new oil-water relative permeability studies, this paper establishes a new relationship between oil-water relative permeability ratio and water saturation. Combined with Leverett function and Welge equation, it deduces the analytical formulae for waterflood frontal water saturation, waterflood post-frontal average water saturation, water-breakthrough average water saturation and oil displacement efficiency, in order to calculate waterflooding indices and automatically draw relative the classic curves. The case study from Qiuling oilfield shows that this analytical method is not only used to calculate the waterflood rontal saturation and other indices, but also draw such classic curves as the oil displacement efficiency vs. injected fluid volumes, water cut vs. injected fluid volumes, etc. References | Related Articles | Metrics

A Comprehensive Production Formula for Horizontal Wells LI Chuanliang, ZHU Suyang, DONG Fengling 2016, 37 (zk(English) ):  78-80.  Abstract ( 52 )   PDF (636KB) ( 115 )   Save Conventional production formulas for horizontal wells only consider the outer planar radial flow and the inner vertical radial flow, and ignore the intermediate planar linear flow. So the flow resistance is underestimated and oil production is overestimated with these formulas. This paper presents a comprehensive production formula for horizontal wells, which covers all the three flows. In comparison with the conventional production formulas, this new formula can get a higher flow resistance and a lower production rate for horizontal wells. Calculations show that the longer the horizontal section is, the higher the ratio of the intermediate planar linear flow to the total flow of wells will be, and the larger the drop of the production rate from the conventional production rate formulas will be. As the horizontal section length is close to the length of oil drainage zone, the new formula tends to be the production rate formula for wells with relatively long horizontal section. Therefore, horizontal wells with long and short horizontal section lengths can be unified by this new formula. References | Related Articles | Metrics

Escaping Loss of Coalbed Methane during Production ZHU Suyang, LI Chuangliang, DU Zhimin, LI Zepei, PENG Xiaolong 2016, 37 (zk(English) ):  81-86.  Abstract ( 58 )   PDF (1125KB) ( 111 )   Save This paper analyzes coalbed methane (CBM) preservation, accumulation, and the escaping loss during production, presents several factors to identify coalbed methane escaping loss by defining two parameters - escaping velocity ratio and escaping distance ratio. Then the escaping loss volume and distribution of CBM escaping are calculated by simulation. Meanwhile, the impact of surrounding rock permeability, initial entrapped gas volume in coal beds and gas production on CBM escaping loss volume are studied. If CBM escaping distance ratio is larger than the maximum CBM escaping velocity ratio, it is considered that CBM will not escape from coal beds. Case calculation shows that the escaping loss is likely to occur in the areas far from wellbore and 10%-15% of CBM reserves will be lost during production, and more than 10% of CBM reserves escapes during the early production stage. Relative low loss commonly occurs in the coal-beds with high and low CBM content, however, the coal-beds with intermediate CBM content may suffer relative high losses. Therefore, the key to reducing CBM escaping loss is to establish producing pressure-drop quickly in coal beds to realize rapid production at the early stage. References | Related Articles | Metrics

Characteristics of Damage of Guar Fracturing Fluid to Reservoir Permeability XU Linjing, ZHANG Shicheng, MA Xinfang 2016, 37 (zk(English) ):  87-90.  Abstract ( 71 )   PDF (587KB) ( 108 )   Save Conventional guar fracturing fluid will damage core permeability after gel-breaking, and influence oil well productivity after fracturing stimulation. Based on the analysis on guar fracturing fluid compositions, dynamic and static adsorption experiments and core-damage experiment are carried out for artificial cores and natural cores. Artificial core-damage experiment result shows that the damage of gel-breaking liquid can be classified into water damage and guar retention damage, of which water damage is more serious than guar retention damage. Adsorption experiment result shows that the retention of the guar molecules of gel-breaking liquid in pores of cores can be classified into adsorption and trapping, accounting for 43.6% and 56.4% in average, respectively. The result from natural core damage experiment in Yuanba area also shows that the gel-breaking liquid in guar fracturing fluid has an aqueous-phase damage to natural cores. Guar molecules after gel-breaking have less impact on permeability of natural cores compared with aqueous-phase damage. References | Related Articles | Metrics

A New Form of Material Balance Equation for Condensate Gas Reservoirs with Oil Rings WANG Nutao, ZHANG Wu, LI Chen 2016, 37 (zk(English) ):  91-95.  Abstract ( 73 )   PDF (738KB) ( 150 )   Save Material balance equation is one of the most commonly-used methods to calculate dynamic reserves of gas reservoirs, but for condensate gas reservoirs with oil rings, their dynamic reserves are not only related to oil and gas production, but also to retrograde condensation degree. Since mass conversion occurs among different products, it is difficult to accurately calculate the amount of conversions and to establish material balance equation with volume balance or molar balance. Also, conversion from wellhead oil and gas flow rate to bottom-hole inflow rate can’t be realized by the direct use of the volume factor and the gas-oil ratio, hence the material balance equation for conventional gas reservoirs greatly differs from that for condensate gas reservoirs with oil rings. On the basis of the law of mass conservation, this paper proposes a general formula of the material balance equation for natural water-drive condensate gas reservoirs with oil rings under production conditions, in which multi-phase flow displacement theory and oil saturations corresponding to curve interpolation are used to get the dynamic reserves of such reservoirs with oil rings by optimizing the objective function through non-linear regression, without converting condensate oil into equivalent gas with empirical formula and without by means of concepts of two-phase deviation factor and state equation of liquid. Therefore, the new formula can avoid the variations in oil and gas components and their volumes resulted from complicated phase changes. The obtained material balance equation has a stronger theoretical foundation and can better reflect the actual status of condensate gas reservoirs. References | Related Articles | Metrics

APPLICATION OF TECHNOLOGY

Reason Analysis and Solution for Log-Seismic Data Discrepancy in 3D Seismic Area:A Case Study of Well Xidi-2 3D Seismic Area in Beisantai Swell, Junggar Basin WEN Tiemin, LUO Xiaoxia, WU Xinxing, LI Daoshan, LI Longmei 2016, 37 (zk(English) ):  96-99.  Abstract ( 71 )   PDF (3677KB) ( 124 )   Save The study of 3D prestack time migration profile of Well Xidi-2 indicates that the time domain profile of the Wutonggou formation as a target zone in drilled well with higher structural position has a bigger t0 compared with well logging data. Such a log-seismic discrepancy occurs from the bottom of Paleogene in this area. The analysis suggests that it is mainly resulted from the lateral velocity changes of the Cenozoic here. Prestack depth migration processing technique is an effective approach for precise imaging of complex structures. This paper uses Kirchhoff integral method to make prestack depth migration processing, and gets the south-north reducing velocity model for the space variation in this area. Finally, the morphology of formation has been corrected, the relative relationship between wells has been recovered, and the problem of the log-seismic data discrepancy has been resolved. References | Related Articles | Metrics

Application of Cloud Transform in Prediction of H Oilfield Carbonate Reservoirs in Middle East CHEN Zhigang, LIU Leisong, GAO Jun, DAI Shuanghe, YANG Yu, HAN Yuchun 2016, 37 (zk(English) ):  100-104.  Abstract ( 67 )   PDF (2576KB) ( 109 )   Save The well production of H oilfield in Middle East has positive correlation with the reservoir permeability, but the seismic wave impedance has nonlinear relationship with the permeability. So using regular linear transform approach to convert the impedance into the permeability is only 50% in accordance rate. Cloud transform is a nonlinear stochastic simulation method, by which the functional relationship between linear deviation points and overall attribute data can be resolved. The procedures are as follows: 1) To select probability function according to the accordance rate between real data probability distribution and simulation prediction results by the function; 2) Aiming to reservoirs and non-reservoirs respectively, to develop the cloud models for impedance-permeability conversion using the function; 3) To convert the impedance into the permeability by using the cloud model. Through the cloud transform, the accordance rate for permeability prediction of H oilfield can reach more than 90%, and this method could be applied to other areas with similar geology conditions. References | Related Articles | Metrics

Quantitative Prediction of Coalbed Gas Content: Technique and Application SHAO Linhai, XU Ligui, LI Xingtao, ZHANG Lei, HUO Lina, DING Qingxiang 2016, 37 (zk(English) ):  105-109.  Abstract ( 74 )   PDF (2886KB) ( 139 )   Save Coalbed gas content is one of the important parameters for coalbed methane (CBM) resource estimation, favorable area evaluation and well deployment. It is related to many factors and difficult to predict. This paper focuses on Baode south area in the north of the eastern Ordos basin. According to the cross plot of logging data and measured gas content of coal core, the density of coal bed is the most relevant factor of gas content, and the relationship between them is derived. Combined with the research of 3D seismic data, the density data and the coal density attribute are obtained by pre-stack simultaneous inversion, and then the lateral distribution of coalbed gas content is predicted quantitatively. The technique applied in the Baode south area in the north of the eastern Ordos basin for quantitative coalbed gas contentprediction can support the research of the coalbed gas content for the favorable area evaluation and the well deployment. References | Related Articles | Metrics

Application of Constraint Analysis Method to Establishing In-Situ Stress Model YANG Minghe, ZHANG Yang, YANG Hu, WEN Qianbin, SHI Jiangang, CHEN Weifeng 2016, 37 (zk(English) ):  110-114.  Abstract ( 62 )   PDF (839KB) ( 136 )   Save The accurate establishment of in-situ stress model is an important basis for oil and gas exploration and development. The constraint analysis method is used to establish in-situ stress model, whose essence is to analyze the constraint boundaries of vertical principal stress, the max. horizontal principal stress and the min. horizontal principal stress, narrow the computing boundaries and improve computing accuracy. On the basis of the fault pattern theory proposed by E. M. Anderson, 4 types of in-situ stress boundaries and the corresponding constraint equations are obtained. The frictional strength on the original fault surface determines the upper limit of stress differences between the max. and min. horizontal principal stress; formation pore pressure can give the lower limit of the min. horizontal principal stress; the width of borehole breakout or drilling-induced fractures can be used to determine the upper limit of the max. horizontal principal stress; the min. horizontal principal stress can be measured by hydraulic fracturing tests and the max. horizontal principal stress can be estimated as well; the vertical principal stress can be gained through density logging curve integral. The actual application shows that the constraint analysis method is an effective way to establish in-situ stress model and to determine the 3 principal stresses (especially the max. horizontal principal stress) combined with the results from laboratory stress experiments. References | Related Articles | Metrics

OIL AND GAS GEOLOGY ABROAD

Genesis of Inclined Water-Oil Contact in Nahr Umr Reservoir, Rumaila Oilfield ZHOU Jiasheng, XIE Jingbin, LIN Jian 2016, 37 (zk(English) ):  115-118.  Abstract ( 73 )   PDF (1729KB) ( 298 )   Save To understand the genesis of inclined water-oil contact (WOC) in Nahr Umr clastic reservoir of Albian stage in Rumaila oilfield and improve the accuracy of oil and gas reserves estimation and rationality of development plan and adjustment, four aspects are discussed including formation water discharge, inclination degree of water-oil contact, response characteristics of oil and water pressure gradient and regional pressure variation by analyzing the data of well logging, wireline formation pressure and regional geology, based on the summaries of different causes of inclined WOCs. It is considered that hydrodynamism is the main reason for the inclination of WOC in clastic reservoir of Albian Nahr Umr formation and the hydrodynamic force is sourced from the surface water supply in Teros-Zagros thrust-fault fold belt in the northeastern part of the oilfield. References | Related Articles | Metrics