Petroleum Exploration and Development

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Petroleum exploration and development practices of sedimentary basins in China and research progress of sedimentology

Sun Longde; Fang Chaoliang; Li Feng; Zhu Rukai and He Dongbo

, 2010, 37(4): 1830-0.

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Based on the characteristics of recent discoveries in China, continental clastic reservoirs are the most important area for reserves and production growth. Significant progress has been made in exploration of carbonates reservoirs, for example, platform-margin reef complexes and platform interior reefs and banks. Volcanic reservoir exploration in sedimentary basins is feasible now. Mature oilfields with high water cut are predominant in the oil production in China. Some technological problems facing the stable production of mature oilfields have been solved by fine characterization of reservoirs, improving water flooding conditions, and EOR techniques. CNPC makes progress on studies of the sedimentary pattern of continental lacustrine basin shallow water delta, the origin and distribution of sandy debris flow, the mechanism and distribution prediction of deep favorable reservoirs, the sedimentary facies evaluation and reservoir prediction of low-porosity and low-permeability conglomerates, the lithofacies palaeogeography reconstruction of marine carbonates, the fine characterization of carbonates platform margins, the mechanism of carbonate reservoir superposition and rework, the origin classification of karst reservoirs, unconventional reservoir evaluation, reservoir improvement techniques, etc. These provide important theoretical and technical support for the exploration and development of oil and gas.

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Distribution of Carboniferous source rocks and petroleum systems in the Junggar Basin

He Dengfa; Chen Xinfa; Kuang Jun; Yuan Hang; Fan Chun; Tang Yong and Wu Xiaozhi

, 2010, 37(4): 1831-0.

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With pre-Cambrian continental nuclei and Early Paleozoic accretionary folded belts as the collaged basement, the Junggar Basin underwent an evolution of intra-cratonic basin after the transitional period of Carboniferous to Permian. The Carboniferous Period was a critical phase for the cratonization of Junggar Terrane, with two continental passive margins developed on both the southern and northern margins, and with rifts and upswells in the basin interior. The rifts were full-filled with volcanic clastic rocks up to 2 000 to 5 000 m in thickness. Influenced by the marine transgression, the regional extended source-rocks of the Lower Carboniferous Dishuiquan Formation(C1d) and the Upper Carboniferous Batamayneishan Formation(C2b) occurred within or around the basin, with the former one as oil and gas source rocks, while the latter one as effective gas source rocks. Volcanic rocks in the Batamayneishan Formation are the main reservoirs. Two petroleum systems were formed: C1d-C (.) and C2b-C2b (!). The tectonic events in the Late Jurassic and Neogene gave rise to the formation, modification, and finalizing of the Carboniferous prospects. The difference between the evolutionary process of each structural unit resulted in the differentiation of the petroleum systems horizontally. A series of oil and gas fields have been discovered in Carboniferous, such as the Wucaiwan, Shixi, Kelameili, and Chepaizi oil and gas fields as well as the oil-bearing Block-2,4,and 6 in the Karamay Oilfield. The exploration has proven that the Carboniferous has great potential for oil and gas discovery.

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Characteristics and controlling factors of the Upper Ordovician petroleum reservoirs in the Tazhong No.1 fault belt, Tarim Basin

Chen Zhijun; Liu Luofu; Wang Weili; Wang Ping; Li Yan; Xiang Caifu; Jiang Zhenxue and Pang Xiongqi

, 2010, 37(4): 1840-0.

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Characteristics and controlling factors of the Upper Ordovician reef-shoal complex petroleum reservoirs in the No.1 fault belt of the Tazhong area were analyzed systematically by studying the distribution and fluid parameters of the hydrocarbon reservoirs. The hydrocarbon reservoirs are characterized by “gas in the outer belt and oil in the inner belt”. Crude oil has low density, low viscosity, high wax content, middle-low sulfur content, and highly varied oil/gas ratio. Natural gas is generally dry gas with high H2S content. An in-depth study of the controlling factors such as reservoirs, source faults, and structures reveals that reservoir beds control oil as a whole and structures control oil locally in the Tazhong No.1 fault belt. Faults pertinent to oil source is crucial, and channels of gas intrusion affect the distribution of hydrocarbons. The exploration of reef-shoal complexes in the Tazhong No.1 fault belt is supposed to focus on the seeking of favorable reservoirs with faults connecting oil-gas source and local high structures.

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Characteristics of energy fields and the hydrocarbon migration-accumulation in deep strata of Tahe Oilfield， Tarim Basin， NW China

Bian Ruikang; Zhang Jinchuan; Tang Xuan; Yun Lu; Jiang Shengling; Zhang Peixian; Guo Huaqiang and Wang Zongyu

, 2010, 37(4): 1841-0.

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Deep energy fields in the Tahe Oilfield are studied and the relationship between energy fields and hydrocarbon migration and accumulation is discussed through the comprehensive analyses of energy field characteristics. Multi-phase tectonic stresses are the main controlling factor of the developmental morphologies of the present fractures. The characteristics of the present regional tectonic stress indicate that the Tahe Oilfield is a favorable area for hydrocarbon collection. The present pressure field of the Ordovician is a slightly low abnormal pressure system. The fluid potential characteristics show that there are two hydrocarbon migration trends: one is from east to west in part of the eastern area, and the other is from south to north in the whole southern area. The present formation water is of typical CaCl2 type. According to the formation water geochemistry, the Tahe Oilfield has a good seal capability, favorable for hydrocarbon accumulation and preservation. Aqueous inclusions indicate that homogenization temperatures are mainly 80-100 ℃, 120-130 ℃, and 150-170 ℃, therein, 80-100 ℃ and 120-130 ℃ represent two large scale hydrocarbon accumulation phases, Early Hercynian and Himalayan, and 150-170 ℃ is controlled by tectonic event and Permian magmatic activities, representing a partial hydrocarbon accumulation event.

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Lake-bottom hydrothermal activities and their influences on the high-quality source rock development: A case from Chang 7 source rocks in Ordos Basin

Zhang Wenzheng; Yang Hua; Xie Liqin and Yang Yihua

, 2010, 37(4): 1842-0.

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By optical microscope and SEM-energy spectrometer, some phenomena that relate to lake-bottom hydrothermal activities, such as siliceous rocks, ankerite laminar deposits, the marcasite brassil anhydrite symbiosis system, and the authigenetic albite filling in early diagenetic slots, have been discovered in Chang 7 high-quality source beds of the Yanchang Formation, Ordos Basin. Various geochemical data of the Chang 7 high-quality source rocks testify further to the existence of lake-bottom hydrothermal activities, and they include abnormally abundant S2- content (on average 7.37%), Mo, Cu, U, and Mn positive anomalies, high ratio of U to Th, positive carbon isotope composition of crystallite ankerite (δ13C from 2.88‰ to 3.03‰), light oxygen isotope composition (δ18OPDB from －16.41‰ to －16.17‰), the enrichment of microelements like Cu and Mn, heavy sulfur isotope composition of strawberry-shaped pyrite (δ34SCDT from 2.37‰ to 5.90‰). In the early sedimentary period of Chang 7, the activation of floor ruptures by violent regional structure-activities was a dynamic factor that produced lake-bottom hydrothermal activities and the hydrothermal activities played an important role in accelerating the extensive development of Chang 7 high-quality source rocks.

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Resistivity correction for drilling fluid invasion using LWD and wire-line logging data: A case from high-porosity and low-permeability

Tian Zhongyuan; Jiang Aming; Yan Weilin; Liu Yingming and Guo Shuangsheng

, 2010, 37(4): 1843-0.

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The effect of drilling fluid invasion on the resistivity of oil-bearing zones during the period from penetrating the zone to completion well logging was studied using intergraded logging while drilling (LWD) and wire-line log data. The results indicate that resistivity change during invasion responds to some important factors such as porosity, oil saturation, pressure differential between drilling mud column and formation, mud filtrate salinity and invasion time. It increases as an exponential function of porosity, a logarithmic function of pressure differential, and a power function of invasion time and oil saturation. Based on the LWD and MDT data, the corrected resistivity equation subject to the drilling fluid invasion was acquired. With the equation, the oil saturation (So) increases by 6.3%-20.0%, averaging at 10.2%.

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Electric field responses of different gas hydrate models excited by a horizontal electric dipole source with changing arrangements

Deng Ming; Wei Wenbo; Zhang Wenbo; Sheng Yan; Li Yanjun and Wang Meng

, 2010, 37(4): 1844-0.

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The exploration of marine controlled source electromagnetic survey for gas hydrate generally consists of a dynamic horizontal electric dipole source towed in the sea water and a static receiver array allocated on the seafloor. In this paper, two orthogonal horizontal components of electric field excited by a horizontal electric dipole source upon one-dimensional horizontal-layered seafloor are calculated to study the effect of different arrangements and gas hydrate models on the response of electric field. There are several dominant factors determining the variation of induced field, including transmitting frequency of the source, distance between the source and the seafloor, water depth, thickness of the overburden layer, as well as physical and chemical structure of the gas hydrate model. Modeling results suggest that the amplitude of received electric fields can reach up to 10－16～10－10 V /(A·m2) by adjusting transmitting frequency; keeping the source being towed several tens of meters above the seafloor can improve the survey efficiency but not decrease the quality of collected data; deep water environment and shallow thin overburden layer are favorable for the survey because of their attribution to signal-to-noise ratio; the porosity and saturation of gas hydrate have significant influence on medium resistivity-the higher resistivity the medium has, the bigger the amplitude of electric field response will be. Forward modeling can provide valuable information for the development of instruments and the design of survey to detect gas hydrate.

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A fine assessment technology for medium-high exploration degree plays

Mi Shiyun; Guo Qiulin; Xie Hongbing; Yang Qiulin and Chen Ningsheng

, 2010, 37(4): 1845-0.

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The current evaluation methods mainly focus on plays without hydrocarbon discoveries. By integrating three techniques, i.e., spatial quantitative prediction technology of hydrocarbon occurrence probability, overlapping processing technology for multi-layer spatial hydrocarbon occurrence probability, petroleum resources abundance fractal simulation restricted by corresponding spatial hydrocarbon occurrence probability, a new fine evaluation method was put forward. This method, based on spatial grids and combining planar and vertical evaluation results, focuses on the assessment of multi-layer plays. Compared with the present methods, it has advantages such as comprehensive assessment, precise processing results, comprehensive data collection and application, exploration effectiveness. By this Method, 38 secondary structural belts in the middle-upper exploration formations in the Turpan-Hami Basin were evaluated. Favorable drilling areas in each belts were pointed out based on the spatial probability of hydrocarbon occurrence. Their corresponding geological favorability index and residual oil resources revealed that the Shengbei, Huoyanshan, Lukeqin, Shanle Structural Belts are the most favorable belts for exploration.

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Monte Carlo simulation for C/O spectroscopy logging while drilling in the horizontal well

Zhang Feng; Dong Jingli; Jia Yan; Xu Yujun and Wang Xinguang

, 2010, 37(4): 1846-0.

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C/O logging is a main logging method that can determine oil saturation. The oil saturation of initial formation can be determined by C/O according to the inelastic gamma spectroscopy in LWD (logging while drilling). The inelastic gamma spectrum were simulated using the Monte Carlo method under the condition of different lithology, porosity, saturation, borehole size, mud and mud invasion, water salinity, shale content, hydrocarbon and source-receiver spacing in horizontal wells. The response of C/O and porosity and saturation was studied, and the effects of several factors on C/O values were given. It is concluded that the relationship of C/O value and oil saturation is linear. C/O values are high when with oil-based mud in boreholes or in limestone formation. The smaller the hole size, the higher the formation water salinity, the more the shale content in the matrix and the bigger the spacing, the greater the formation C/O value. C/O values are affected differently as mud invasion depth, lithology, porosity and drilling mud change. It is favorable to identify formation fluid by using C/O spectroscopy logging under the condition of small mud invasion depth, small borehole size, high porosity and heavy oil.

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Fine description and geologic modeling for volcanic gas reservoirs

Song Xinmin; Ran Qiquan; Sun Yuanhui; Wang Yongjun; Yan Lin and Chen Fuli

, 2010, 37(4): 1847-0.

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To understand the geology of volcanic gas reservoir development, research was carried out on volcanic rock, body lithology, lithofacies, fractures, gas and water zones, reservoir classification, and geologic modeling for volcanic gas reservoirs. The volcanic rock body identification and anatomy reveals the spacial distribution and geometric parameters of volcanic rock body. The lithology and lithofacies research shows that, favorable lithology of volcanic rock includes volcanic breccia, vesicular basalt, vesicular ryolite and breccia lava, and favorable lithofacies includes air fall and spatter subfacies of explosive facies, and upper and lower subfacies of effusive facies. Based on FMI imaging, nuclear magnetic logging and traditional logging methods, fracture parameters were interpreted. By use of coherence, curvity and dip angle methods, comprehensive fracture prediction were performed, which reveals the distribution of fractures in volcanic rock. Nuclear magnetic, dublet transverse wave and traditional logging data were applied to identify gas and water zones, with the conformity ratio up to 90%. The prediction research on reservoir classification based on “volume control” indicates the spacial distribution of volcanic reservoirs. By means of volume control structure modeling and seismic control attribute modeling, models of structure, framework, matrix and fracture parameters for volcanic dual-media reservoir were built.

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Miscible conditions of CO2 flooding technology used in low permeability reserviors

Liu Yuzhang and Chen Xinglong

, 2010, 37(4): 1849-0.

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Whether CO2 and crude oil in reservoirs are able to be in a miscible state is important in CO2 flooding. Minimum miscibility pressure (MMP) measured by the interfacial tension method is greatly different from that measured by slim tube experiment. The effects of pore structure on crude oil relative volume and density of CO2 show that the pore structure of porous media can affect liquid physical characteristics. Using the MMP measured by slim tube experiments as a MMP in reservoirs need to be proved and improved. Analysis of some major factors affecting miscible conditions reveals that pore structure, formation pressure and injection flow rate affect the MMP of CO2-crude oil in porous media. MMP in porous media decreases with core permeability decrease. A reservoir with low average formation pressures has a relatively low measurement MMP. Lower measurement MMP can be obtained by optimizing flow rate. According to the three factors analyzed above, a equation is formed to calculate MMP in porous media, which makes the pressure curve more precise. Fluid state can be described between different pressures.

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Displacement mechanisms of air injection in low permeability reservoirs

Jiang Youwei; Zhang Yitang; Liu Shangqi; Guan Wenlong; Chen Yaping and Liu Shuangmao

, 2010, 37(4): 1850-0.

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By means of physical modeling and numerical simulation, this paper makes a systematic study on oil displacement mechanism by air injection in low permeability reservoirs. Based on the findings, production performance by air drive is studied through the application of a real low permeability reservoir model. Studies show that air intake capacity is far greater than water intake capacity in low permeability reservoirs. Therefore, air injection, which can effectively supplement and maintain reservoir pressure, can build effective pressure displacement system much easier than water injection. Low-temperature oxidization reaction will occur between oil and the oxygen in air, which consumes oxygen and forms nitrogen drive. At the same time, CO2 and large amounts of heat are generated, and the temperature in some parts of the reservoir can reach about 200 ℃. Nitrogen drive contributes 69%; temperature increasing and CO2 generation contribute 26.7% and 4.3% respectively for the total recovery of air drive. Recovery factors by air drive, nitrogen drive and water drive are also studied respectively by using the real low permeability reservoir model. Recovery factor by air drive for 30 years reaches 21.5%, and it is twice as large as that of water drive, which is 10.6% for the same period. Production performance is significantly improved. Air drive is an effective way for improving production performance and increasing recovery factor.

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Synthesis and property evaluation of a salt- and alkali-resistant star-polymer

Luo Wenli; Han Dong; Wei Li; Lin Qingxia and Fan Jian

, 2010, 37(4): 1851-0.

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A salt-and alkali-resistant star-polymer was made by graft β-CD functional monomer and acrylamide monomer copolymerization and post-hydrolysis. The optimum parameters: azobisisobutyronitrile concentration of 50 mg/L, the mass fraction of acrylamide 25%, the graft β-CD functional monomer mass fraction of 1.5%, initiating temperature 5 ℃, hydrolysis temperature 90 ℃ and hydrolysis 3 hours. The atomic force microscope and infrared spectroscopy morphology characterization results show that: the star-polymer S07313 contains the star-nuclear of the graft β-CD functional monomer. The molecular weight of the star-polymer S07313 is 24.5 million, other basic physical and chemical properties can meet the technical requirements of application in oil fields. With the addition of NaOH mass fraction of 1.0% in the Daqing simulated brine, the apparent viscosities of the star-polymer S07313, HPAM3000 and MO4000 are 42.40 mPa·s, 29.20 mPa·s and 18.00 mPa·s. The star-polymer S07313 and surface active agents Alkylbenzene Sulfonate have an excellent compatibility.

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Application of reservoir structure research in the fine exploitation of oilfields

Zeng Xiangping

, 2010, 37(4): 1852-0.

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Gudao Oilfield in the Shengli oil area, as a typical strong heterogeneous sandstone reservoir of fluvial facies, has successfully applied the reservoir configuration theory to describe reservoirs finely in the extra-high water cut stage. It finely divided the structural levels of reservoir: the original single layer sandstone and mono-sand body are further divided into single-origin monosandstone bodies. The effect of internal configurations and micro-geologic interfaces in sandstones on the remaining oil distribution was studied, achieving favorable effects on exploiting adjustment and tapping potential. Practices proved: (1) the internal structure is complicated in marginal banks and channel bars in thick layers of the main stream channel, and the interlayers in lateral depositions and dropping silts have some separation characteristics, favorable for horizontal wells to tap remaining oil in the top of thick layers; (2) the upper overbank deposits in the double structure of fluvial facies and the thin sandstone layers in marginal abandoned stream channels, which have relative poor physical properties and low exploiting degree, are all important potential areas at the later period of development; (3) abandoned stream channels existing inside the complex curving-flow zones of the reservoir form semi-connection or no connection, affecting the effect of development, and analyzing and identifying them are helpful to improve the corresponding relationship between the injection and production; (4) a single-origin sandbody can be divided into several flow units, and analyzing their difference in the flow characteristics can help to treat the water invasion of reservoir.

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Scale inhibition in injection water with magnetic treatment in Xifeng Oilfield

Wu Jiazhong; Liu Yuzhang; Wei Li; Wu Kangyun; Lin Qingxia; Liu Li and Zhang Jianguo

, 2010, 37(4): 1853-0.

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Taking the injected water in the Xifeng Oilfield as the object, the anti-scaling effect of magnetic treatment under different temperatures, flowing velocities, deposit time intervals and magnetic field intensities was studied. The variation rule of the water molecule aggregate microstructure before and after magnetic treatment and the scale inhibition mechanism were also discussed. The result showed that magnetic field strength, water velocity, temperature and delay time all affect the result of anti-scaling, among which temperature has the most influence. For the water sample containing 1 800 mg/L of Ca2+, the ratio of scale inhibition is 9.66% under the conditions of reservoir temperature, magnetic field strength of 99.22 A/m(7 900 Oe), and water velocity of 5 mL/min. However, the ratio of scale inhibition is as high as 85.34% under the room temperature. Under external magnetic field, hydrogen bond was disturbed, leading to the weakening of the electrophilic action which gathers the hydrogen atom in aggregate water molecule. That would be favorable for the dispersion of the water molecule aggregate and can greatly decrease the aggregation of scaling ions.

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A deep-sea pipeline pose measurement system and its control strategy

Wang Liquan; Wang Wenming; Zhao Dongyan and He Ning

, 2010, 37(4): 1854-0.

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The tie-in operation of two deep-sea pipelines needs to measure the relative position of two flange centers, and needs to prefabricate the transition pipeline section. Aimed at deep-sea environment in China, a deep-sea pipeline tie-in pose measurement system was designed based on stretching-wire measurement devices. The matrix pose algorithm was applied to calculate the vector of stretching-wire length, the transition angle, the transition matrix, etc., achieving the vector solution of two flange centers. Control strategies for the corresponding measurement parameters and the actual operation were also analyzed. Deep-sea pipeline pose measurement system can accurately obtain distance and relative angle information of two pipelines which is to be connected, and is the essential tool of deep-sea Tie-in, and has great significance for the deep-sea flange connection operation.

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Remote sensing for the sea ice effect monitoring in petroleum development: Take the Nanpu sea area as an example

Zhou Hongying; Yu Wuyi; Zhang Yimin and Wang Wenhui

, 2010, 37(4): 1855-0.

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Sea ice monitoring is one of the important guarantees for marine operation and transport. The space borne remote sensing techniques have the advantages of wide area surveillance, multi-temporal resolution, prompt acquisition, and high precision. They have become one of the key sea ice monitoring techniques. The new Chinese satellite HJ-1A/B CCD images were used in the sea ice monitoring of the Nanpu sea area in winter, during the time from Nov. 29, 2008 to Feb. 21, 2009. A fast processing work flow was established based on the object-oriented information extraction technology. It was used to map the change of the ice area during the period. According to the ice area change, the ice sea distribution, and the historical meteorological information, the ice period was divided into: initial ice forming (early Dec., 2008 to the end of Dec., 2008), abounding ice (from the end of Dec., 2008 to the end of Jan., 2009), ice thawing (from the end of Jan., 2009 to the end of Feb., 2009). The work contributes to the safe construction of the artificial islands in the Nanpu-4 structure during the icebound season. The study shows that the remote sensing technology is a practical and effective technical means for the sea ice security monitoring of oil fields’ exploration, development and engineering construction in beaches.

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Relationship between methylphenanthrene index, methylphenanthrene ratio and organic thermal evolution： Take the northern margin of Qaidam Basin as an example

Chen Yan; Bao Jianping; Liu Zhaoqian; Wang Liqun; Deng Kui; Wang Yanping; Qi Wenzhen; Gao Xuefeng and Jin Chunhua

, 2010, 37(4): 1856-0.

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Based on the study of thermal simulation of Jurassic immature and low mature source rock in the northern margin of Qaidam Basin, this paper builds up the relationships between methylphenanthrene ratio, methylphenanthrene index and vitrinite reflectance of two different types of Type-Ⅱ organic material lacustrine facies source rock (humic-prone and sapropel-prone organic material). The result indicates that there are different relations between methylphenanthrene index and vitrinite reflectance in different stages of organic thermal evolution. The same methylphenanthrene index value corresponds with two different vitrinite reflectance ratios; it will show deviation when adjudging oil maturity; while the methylphenanthrene ratio and vitrinite reflectance ratio have good positive linear correlation. When Ro is between 0.50%-1.80%, the ratio will increase monotonously, and correlation coefficient will be over 0.90. The relation between them during high mature stage is also positive, thus methylphenanthrene ratio is superior to methylphenanthrene index to judge the oil maturity. Then the paper calculates the oil maturity in the northern margin of Qaidam Basin on the basis of the relationships. The result coincides well with the geological backgrounds and the confidence level is high.

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, Volume 37 Issue 4