Lithologic Reservoirs

Shale oil is liquid hydrocarbon reserved in effective argillaceous source rocks with free phase, adsorbed and dissolved phase. Recent years, America has achieved great success in commercial shale oil production, whereas shale oil research in China is still in its infancy with more related theory innovations. Based on shale oil characteristics and experience of American shale oil exploration and development, this paper analyzed and summarized the research progress and some significant cognition in shale oil forming conditions, reservoir features, accumulation mechanism and evaluation method at home and abroad. The systematical comparison of shale oil characteristics between China and America shows that Chinese shale oil mainly deposited in semi-deep and deep lacustrine, and black shale spreads widely, featured by great thickness, complex structures with frequent sandy interbedding. Preferable shale rich in organic matter usually coexists with other lithologies in laminated texture, and the kerogen type of organic matter is predominantly sapropelic with Ro of 0.5%～1.2% and TOC more than 2.0%. Relative high content of fine-grained carbonate and clay exceeding 50% results in a poor reserving capacity. Hydrocarbon-generation condition and reserving capacity significantly control lacustrine shale oil accumulation, simultaneously with additional preserving conditions taken into account in strong tectonic activity areas, such as in the rifted basins. Mixed-type and fractured-type shale oil overall have a huge exploration potential, and the matrix-type follows. In order to promote shale oil research and realize shale oil production earlier in China, the fundamental researches should be on the basis of theories study, and prominently focus on hydrocarbon occurrence, micro pore structure, retained oil accumulation mechanism, structurepreserving condition, evaluation system and resource evaluation method. The purpose of these studies is to provide theoretical guidance for the high efficient exploitation of shale oil in China.

Fracture spacing optimization for horizontal well alternating fracturing and influencing factors

YANG Zhaozhong, SU Zhou, LI Xiaogang, ZHANG Cheng, XIE Zhongcheng, DENG Ke

2015, Vol.27(3): 11–17 Abstract ( 488 ) PDF (723 KB) ( 404 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.002

For creation of large-scale effective complex fracture networks of unconventional oil/gas plays, fracture spacing for alternating fracturing should be optimized. Started from the effect of total induced stresses on initial horizontal stress anisotropy, the total induced stresses computational model of two adjacent hydraulic fractures with different fracture height and fracture net pressure was built. Subsequently, optimization approaches for critical fracture spacing of the first two hydraulic fractures and optimal fracture initiation position of the third one were proposed. The analysis result shows that critical fracture spacing between the first two hydraulic fractures decreased with the increase of Poisson’s ratio, and increased with the increase of fracture height and fracture net pressure; the optimal fracture initiation position of the third fracture apart from the first one decreased with the increase of Poisson’s ratio, and increased with the increase of fracture height. However, fracture net pressure has negligible impact on the optimal fracture initiation position of the third fracture. Finally, with comparison and analysis of a case study, the optimization results of the proposed approaches were proved to be much more advantageous and economic over the existed one, which is of significant guidance for creation of complex fracture networks with alternating fracturing technology in unconventional oil/gas reservoirs.

Application of experimental analysis technology to research of tight reservoir in Jimsar Sag

JIN Jun, XIANG Baoli, YANG Zhao, LI Lulu, LU Daoping, ZHANG Yi

2015, Vol.27(3): 18–25 Abstract ( 581 ) PDF (2353 KB) ( 433 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.003

The reservoirs of Lucaogou Formation in Jimsar Sag of Junggar Basin distributed alternately in high quality source rock layer series. There are two sets of unconventional reservoirs in the upper and lower segments and show typical tight oil characteristics of various lithologies, strong heterogeneity and micron-nanometer pore with oil. The original experimental analysis technology for conventional reservoirs is not satisfied for the need of further exploration and development of tight oil. Based on targeted experimental analysis technology, such as coordinated measurement of multi-parameter, exploration of wash oil, measurement of porosity-permeability and wettability of tight oil core and staining technique of carbonate minerals, this paper studied the typical tight oil characteristics of lithologies, physical properties, oiliness and their inherent correlation. The new achievements not only provide aboundant experimental materials to deepen geological understanding for the tight oil of Lucaogou Formation in the Jimsar Sag, but also effectively promote the exploration and development in this area.

Exploration potential of tight oil of the Paleogene and Neogene in western Qaidam Basin

WAN Chuanzhi, WANG Peng, XUE Jianqin, SU Xueying, ZHOU Gang, GOU Yingchun

2015, Vol.27(3): 26–31 Abstract ( 628 ) PDF (2197 KB) ( 470 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.004

The Paleogene Lower Ganchaigou Formation and Neogene Upper Ganchaigou Formation in the western Qaidam Basin have the basic geological conditions to form tight oil. The organic carbon content of effective hydrocarbon source rocks in the upper segment of Lower Ganchaigou Formation is between 0.8% and 2.0%, and the type of organic matter is mainly Ⅰ-Ⅱ1. The organic carbon content of effective hydrocarbon source rocks in Upper Ganchaigou Formation is between 0.6% and 1.5%, and the type of organic matter is mainly Ⅰ-Ⅱ1. Thermal simulation experiment shows that it is in the main stage of hydrocarbon generation of Paleogene-Neogene in western Qaidam Basin when the Ro of source rocks is between 0.47% and 1.30%, and liquid hydrocarbon yield reaches maximum when Ro is 0.746%. Sedimentary facies study indicates that extensively developed semi deep-deep lake facies source rocks of the Paleogene Lower Ganchaigou Formation and Neogene Upper Ganchaigou Formation has source-reservoir symbiotic relation with shore shallow lake facies sand bodies or carbonate rocks, which is beneficial to form tight oil, and ramp area of paleostructure and the center of source sag are favorable for tight oil enrichment. The Neogene Upper Ganchaigou Formation in Zhahaquan Sag-Wunan ramp area, Upper Ganchaigou Formation and Lower Youshashan Formation in NanyishanXiaoliangshanarea and the upper segment of Lower Ganchaigou Formation in Qigequan-Yuejin ramp area are the three favorable exploration zones for tight oil.

Lacustrine “ white smoke type ” exhalative rock — A new type of tight oil reservoir: A case study from Lower Permian Fengcheng Formation in Urho area, western margin of Junggar Basin

FU Rao, ZHENG Rongcai, CHANG Hailiang, QI Liqi, WEN Huaguo, LI Yun

2015, Vol.27(3): 32–42 Abstract ( 577 ) PDF (2637 KB) ( 431 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.005

As the representative of tight oil reservoir of Lower Permian Fengcheng Formation in Urho area, western margin of Junggar Basin, dolomitized rocks has great potential for oil and gas exploration and development of the “whitesmoke type” exhalative rock tight oil reservoir. Based on core observation and description, thin section analysis, scanning electron microscope, X ray diffraction and property analysis data, under the guidance of hot water sedimentary theory, this paper discussed the causes of these characteristics of tight oil reservoir, proposed mixed sedimentary model of volcanic eruption-sublacustrine hydrothermal jet flow—“internal and external sources”. The development and distribution of reservoir are controlled by four factors: （1）the semi deep lake-deep lake environment laid material foundation for the development of sublacustrine exhalative rock tight oil reservoir; （2）tectonic disruption and dissolution improved reservoir and the formation of “sweets” in tight oil reservoir; （3）the regional distribution of exhalative rock tight oil reservoir is controlled by regional tectonic framework and tectonic inheritance activities, provides the volcano hydrothermal fluid, diagenetic dissolution and alteration and migration of oil and gas accumulation in channel; （4）the semi-deep to deep lacustrine facies “white smoke type” exhalative rock areas with multi-phase tectonic fracture and thermal dissolution is favorable tight oil reservoir “sweets” location, but also for the prediction of target of dense reservoir.

Genetic types and controlling factors of Paleogene sand bodies in Chunguang Oilfield

LI Weicai, FAN Zhonghai, YANG Xiaopei, WANG Yuchen, MA Kuixiang

2015, Vol.27(3): 43–48 Abstract ( 453 ) PDF (1445 KB) ( 593 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.006

Chunguang Oilfield is located at Chepaizi uplift in western Junggar Basin, and its thin sand body and various genetic types made the reservoir distribution hard to predict. Based on composite analyses of three dimensional seismic, well logging, core and analysis assay data, combined with high resolution sequence stratigraphy method, this paper established sequence stratigraphy framork of Paleogene, divided the genetic types of sand bodies, and concluded the identification signs of different types of sand bodies from the aspects of lithologies, sedimentary thickness and distribution features. Through the control effects of water depth, sediment supply, hydrodynamic conditions and formation development style, the sand body types and distribution rule were discussed and the genetic model of Paleocene sand bodies in Chunguang Oilfield were established. The results show that the Paleogene in Chunguang Oilfield developed braided river delta and lake facies, braided river delta front, front delta and coastal shallow-lake subfacies are developed,and the genetic types of sand bodies mainly are underwater distributary channel, front sheet sand and bank bars. Flat terrain, abundant source rocks, changes of lake-level and wave transformation are the main controlling factors for the genesis of Paleogene sand bodies.

Hydrodynamic characteristics and geological significance of estuaries of inland lake delta

QI Yalin, LIU Xianyang, YANG Shiyu, ZHANG Tao, LI Chengshan, XIE Xiankui

2015, Vol.27(3): 49–55 Abstract ( 620 ) PDF (647 KB) ( 537 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.007

Analysis of hydrodynamic characteristics of estuaries is important premise and means for understanding sedimentary process, effective revealing deposition mechanism and model, reasonable characterizing sand body morphology. Jet theory and Newton internal friction law of fluid mechanics were applied to analyze hydrodynamic characteristics and dominant mechanism of estuary and hydrodynamic field respectively．The results show that after rivers into lake, the resistance suffered from lake water body derived from viscous force or internal friction force which produced by relative motion of river water body and lake water body, the greater the average flow velocity of river water body is, the more shallow the lake water body is, the greater the velocity gradient is, and the greater the internal friction or shear stress. The propulsion length of natural river water into the lake water is limited, which depends on the initial velocity and depth rather than width of exit section of river water. Tongue shaped mouth bar sand body distributed parallel to coast developed in estuaries of lake delta front rather than underwater distributary channel sand body. The complex and varied sand body morphology in estuaries is essentially resulted from the overlaying and joining together of multiphase plain channel sand body distributed vertical to shorelines and underwater mouth bar sand body distributed parallel to shorelines.

Crucial period of water-soluble gas degasification ： A case study from Shaximiao Formation in Chengdu Depression

YANG Yingtao, LI Qi, ZHANG Shihua, ZHU Li

2015, Vol.27(3): 56–60 Abstract ( 461 ) PDF (614 KB) ( 597 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.008

The water-soluble gas degasification and accumulation is the key issue of many oil geological workers, especially the crucial period of the water-soluble gas degasification. If have good condition of reservoir, trap and preservation in that period, the gas can accumulate. By means of the analyzing data of inclusion, formation water salinity, temperature and pressure, combining with basin simulation and regression equation of gas solubility, this paper calculated the gas solubility of Shaximiao Formation at the key periods in Chengdu Depression, and researched the alternation characteristics of gas solubility. The results show that the time from the primary time of hydrocarbon expulsion of the source rocks in the fifth member of Xujiahe Formation to the hydrocarbon accumulation period of Shaximiao Formation, the gas solubility is lowest, which is the key period for the water-soluble gas degasification.

Calculation method of permeability for big pore interval porosity of tight oil reservoir

ZHENG Jiandong, WANG Xiaolian

2015, Vol.27(3): 61–65 Abstract ( 651 ) PDF (773 KB) ( 381 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.009

The tight oil reservoir of Fuyu layer in the southern placanticline of Songliao Basin has become more practical exploration breakthrough objective for the sustained and stable yields of Daqing Oilfield. Permeability is an important parameter for evaluating the“sweet spots” of tight oil, and the accurate calculation of permeability is a key technology for parameter evaluation of “seven properties”（lithologies, physical properties, oiliness, electric properties, brittleness, source rock features and ground stress anisotropy） and the deployment and implementation of tight oil exploration and development. Based on the analysis of the inapplicability of several commonly used methods of calculating permeability by logging for tight oil reservoir, combined with experimental data from NMR and mercury intrusion, this paper determined the relationship between different pore size distribution and permeability. Accorded to the largest contribution characteristic of the big pore interval porosity to reservoir permeability, a method of using the big pore interval porosity for calculating permeability was formed. This method improved the calculation precision of logging permeability in tight oil reservoir, and provided a basis for accurate evaluation of tight oil reservoir.

Sedimentary characteristics of shallow water delta of Quan-4 member in Xingcheng area, Songliao Basin

SUN Chunyan, HU Mingyi, HU Zhonggui, XUE Dan, LIU Shiyu

2015, Vol.27(3): 66–74 Abstract ( 461 ) PDF (2139 KB) ( 393 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.010

The fourth member of Quantou Formation in Xingcheng area in Songliao Basin is mainly consisted of mudstone, silty mudstone, pelitic siltstone and siltystone. Based on the analysis of mudstone color, palaeophyte fossil, sedimentary structure and logging facies, the fourth member of Quantou Formation was confirmed as retrograding shallow water delta depositional system which develops delta plain and delta front subfacies, and distributary channel and crevasse splay are the main microfacies. According to the principle of high sequence resolution stratigraphy, this paper divided the sequence of Quan-4 member, combining with the distribution regularity of sandstone and mudstone, prepared the distribution layout of sedimentary facies, and analyzed the regularity of vertical evolution. The result shows that: Quan-4 member can be divided into seven short-term sequences, from Q4-SSC1 to Q4-SSC7. During the Q4-SSC7 period, water reached the deepest, and only developed delta front subfacies; during the period of Q4-SSC1, channel sand body is mostly developed, which is the best period for development of reservoir. In the vertical, Quan-4 member experienced a sedimentary evolution process from shallow to deep water, which is an transformation process from delta plain to delta front, reflecting an lake invasion of the sedimentary process in the study area.

Geological significance and controlling factors of nonhydrocarbon fluid of Jiufotang Formation in Naiman Sag

SHU Lijuan

2015, Vol.27(3): 75–81 Abstract ( 454 ) PDF (1468 KB) ( 474 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.011

The nonhydrocarbon fluid in Naiman Sag of mainly refers to CO2, H2S and N2. Through component analysis of oil-associated gas, combining with regional tectonic history, nonhydrocarbon fluid content and carbon isotopic analysis, this paper studied the genesis, time entering into the reservoir and controlling factors of preservation and distribution of the nonhydrocarbon fluid in Naiman Sag. The result shows that CO2 and H2S in Naiman Sag come from mantle-derived magma eruption, prior to entering the reservoir of oil and gas. The enrichment degree of CO2 in formation water is directly proportional to the concentration of HCO3-. Nature of H2S is not stable, and exists in the form of trace H2S, organic sulfur compounds and pyrite nodules at present. The enrichment degree of H2S and organic sulfur compounds is proportional to the concentration of SO42-. The atmospheric N2 came into the reservoir at the late Yanshan tectonic uplift, and enriched in the vicinity of shallow strata and shallow fault. The distribution characteristics of sand bodies control the plane distribution rule of nonhydrocarbon fluid. Thickness of mudstone and configuration relation between mudstone and sandstone decided the preservation conditions of nonhydrocarbon fluid. The research results provide theoretical basis for next exploration deployment in Naiman Sag.

Discovery of bitumen of Yingshan Formation in GL3 well of Tarim Basin and its geologic significance

MA Qingyou, TIAN Peng, LU Haitao, SHA Xuguang

2015, Vol.27(3): 82–86 Abstract ( 459 ) PDF (1422 KB) ( 521 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.012

Great number of soild bitumen have been found in Yingshan Formation from GL3 well in Guchengxu Uplift of Tarim Basin. It occurred in the vug and fissure of micritic calcarenite and dolomitic limestone. Based on the analyses of core observation, micrograph and coefficient of reflection, we found that bitumen has many characteristics of clear boundary, insoluble in chloroform, no fluorescent display, with coefficient of reflection ranging from 2.76% to 2.85%. This characteristics are similar to pyrobitumen resulted from paleo-reservoir cracking. The discovery of bitumen in Yingshan Formation in GL3 well has two major geological significances: （1） the difference of wave impedance between bitumen development segment and wall rock may be the main reason for string beads reflection in Yingshan Formation in GL3 well, and can cause a deviation of reservoir prediction of; （2） through the analysis of inclusion thermometry, origin of bitumen and gas, burial history and hydrocarbon generation history, we reconstructed the accumulation process of the paleo-reservoir in GL3 well. We can divide the process into two phases: Middle-Late Caledonian paleoreservoir formation and Late Himalayan paleo-reservoir cracking to gas and transforming to pyrobitumen. It is of certain significance to deepening the study of reservoir forming conditions of Guchengxu Uplift.

Relationship between fracture characteristics and “ five-property ” of shale reservoir

YAN Jianping, YAN Yu, SIMA Liqiang, WEN Danni, WEN Xinfang, GENG Bin

2015, Vol.27(3): 87–93 Abstract ( 573 ) PDF (2551 KB) ( 500 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.013

Shale formations are typically characterized by low porosity and low permeability. While, the decisive condition of whether shale formations can be reservoirs is nothing but the existence and development of fracture. Taking shale formations of Funing Formation in Subei Basin as an example, this paper studied the relations of fracture characteristics with lithology, physical properties, oiliness, fracability and electric properties. During the research, petroliferous fractures are easy to found, and it is obvious that the permeability of fractured sample is higher than that of uncracked, which is greater than 10 mD in general. Fracture plays an important role in improving shale permeability and reservoir capabilities. Samples with fractures usually have higher content of calcite and the corresponding lithology is generally calcareous mudstone, limy shale and limy mudstone. The intervals which developed intrinsic fracture have high Young’s modulus, low Poisson’s ratio and high brittleness coefficient. The intervals’ brittleness is strong, and for this reason, these intervals are normally easy fracturing. Using logging response characteristics can easily distinguish fractures with calcite filled and no filling cracks accompany with oil trace. This result provides a basis for identifying effective shale reservoir

Application of fitting stereoscopic Q modeling technology

CUI Hongliang, LIU Zhanjun, WAN Xuejuan, WANG Zedan, CHENG Zhanzhan, ZHANG Xueyin

2015, Vol.27(3): 94–97 Abstract ( 444 ) PDF (1695 KB) ( 637 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.014

Due to the absorption and attenuation in seismic exploration, the received frequency is reduced, which seriously affects the quality of the seismic data. Therefore, the data must be compensated for its decay. VSP data receives the direct wave, and the traveling time is short, so it has high S/N, and Q value calculated by spectral ratio method is more reliable. However, the number of VSP wells within the region is limited, so the calculated Q value can not represent the entire region. This paper presented a combined method to calculate the fitting Q value, which is based on the Li Qingzhong formula. It relies on the exact velocity spectrum picked. This Q value is calculated after VSP calibration data, and creates a variable stereoscopic Q model. By comparing the application of actual data, this fitting Q modeling technology can improve the overall energy and frequency. This calculated Q value is reliable, and this new method is worth of learning.

Prediction technique of high-quality reservoir in tight reservoir of the sixth member of Xujiahe Formation in Jiannan area

ZHANG Shuishan, LIU Yongjiang, LIU Xianhong

2015, Vol.27(3): 98–102 Abstract ( 516 ) PDF (1413 KB) ( 593 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.015

The tight gas reservoir of the sixth member of Xujiahe Formation which is characterized by sandstone-rich, gas-bearing in whole and local enrichment is favorable area for exploration. The sixth member of Xujiahe Formation is chara-cterized by poor physical properties and relatively thin thickness, which gives birth to similar wave impedance of sandstone reservoirs and mudstones. Thus, it is difficult to use post-stack wave impedance inversion to distinguish reservoir. Prediction technique of high-quality reservoir in tight reservoir has been established by technical research. It includes three steps: firstly, seismic facie models of typical geologic bodies should be summarized from logging information and the macroscopic favorable zones ought to be forecasted by analyzing seismic attributes; secondly, physical properties of different types of rocks such as impedance, Poisson’s ratio and so on are supposed to be analyzed by rock physics modeling, in which the sensitive lithology parameters can be picked out; thirdly, favorable reservoir is able to identified effectively by comprehensive application of multi-parameter inversion and pre-stack inversion. The application of this technique in the sixth member of Xujiahe Formation in the study area proved to have good result and have great application prospects.

Application of constrained sparse spike inversion in the third member of Hetaoyuan Formation in Dupo Oilfield

ZHANG Yi, YIN Yanshu

2015, Vol.27(3): 103–107 Abstract ( 532 ) PDF (1162 KB) ( 659 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.016

The reservoir in Dupo Oilfield is controlled by structure and channel sand body, and has fast lateral variation and well developed fracture, which restricts the development of oilfield in the late production. In order to make clear the reservoir distribution characteristics, we need to depict the development and distribution of sand body through seismic inversion technique. Based on the geologic, seismic and logging data, this paper carried out reservoir prediction of ⅡⅥ oil groups of the third member of Hetaoyuan Formation. According to the basic principle of constrained sparse spike inversion, carried out feasibility analysis, well-to-seismic calibration and wavelet extraction, formed frame model by using interpreted formation and fault, then established low frequency model, and finally completed the study on constrained sparse spike inversion by setting important parameters. Through analyzing inversion results, the development and distribution of sand body of the third member of Hetaoyuan Formation in Dupo Oilfield are clear, which depicts the distribution characteristics of reservoir to a certain extent and provides a reference for the next development and adjustment of Dupo Oilfield.

Research and application of high-precision merged static correctiontechnology based on variogram

ZHANG Yongfeng, WANG Peng, ZHANG Yabing, XU Xiaoping, SU Qin, XU Xingrong

2015, Vol.27(3): 108–114 Abstract ( 441 ) PDF (1840 KB) ( 596 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.017

The travel-time curve of seismic refraction waves is distorted by complex surface geological structures and cannot in-phase stack, so we need to carry out static correction of seismic data. Each static correction method has its own application condition: the elevation statics method cannot eliminate the effect of low velocity; the model statics method is limited by the length of alignment and the depth of tracking, so it is difficult to fully reflect the form of lowvelocity zone bottom boundary; the refraction statics method is only applied for areas with flat surface, uniform lateral velocity and significant refractive layers；the tomography statics method is adapted to any surface model inversion, but the inversion results are instability. A certain kind of static correction cannot solve all problems for increasingly complex exploration areas. This paper presented a high-precision three-dimensional static correction method based on variogram fitting reconstruction which is applicable to complex region with a variety of surface types, it can achieve fitting and reconstruction of different statics, solve the problem of different static correction advantage fitting in the complex surface conditions, and effectively improve the image quality of three-dimensional seismic data to ensure the reliability of structural morphology.

Logging evaluation methods of source rocks of tight oil of Upper Ganchaigou Formation in Zhahaquan area

ZHENG Xi, ZHANG Xiaoli, WANG Guomin, DU Jiangmin, ZHANG Zijie, ZHONG Gaorun

2015, Vol.27(3): 115–121 Abstract ( 480 ) PDF (1067 KB) ( 271 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.018

In recent years, there have been found large-scale distribution of tight oil reservoir in the lower member of Upper Ganchaigou Formation（N1g） in Zhahaquan area of Qaidam Basin, but the source-reservoir configuration is not clear. So it has an urgent need to establish effective source rock evaluation method. Based on source rock coring materials and comparative analysis of laboratory data with conventional logging response, the resistivity, acoustic and Uranium are proved to be the sensitive parameters reflecting the organic matter abundance of source rocks. ΔlgR method and Uranium-TOC regression method were used to establish qualitative and quantitative interpretation model. At the same time, the method of evaluating the organic matter abundance through Litho Scanner was explored. The quantitative interpretation model according to Uranium-TOC regression method is proved to be the most efficient way to reflecting the change trend of TOC of the lower member of Upper N1g in Zhahaquan area, and the calculation is simple and convenient, so it can provide a reliable basis for evaluating the source rocks of the tight oil in this area. The calculation accuracy of TOC according to Litho Scanner is slightly lower affected by the geological condition of this area, but this method is not controlled by regional environmental factors, and can be widely used in fine interpretation of lithology and source rocks of reservoirs in different areas.

Research on mean velocity field modeling method for low velocity anomaly zone: A case study from Q oilfield, Bohai

BIAN Li’en, YU Qian, GU Zhimeng, HAN Zijun, QU Yong

2015, Vol.27(3): 122–126 Abstract ( 437 ) PDF (1165 KB) ( 660 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.019

As the bridge to connect seismic and geological, time-depth conversion is a hot topic of geophysical research. In recent years, with further exploration and exploitation of Bohai Oilfield, higher accuracy of time-depth conversion is required. The target zone of Q oilfield is the deposition of meandering river of Minghuazhen Formation, and it is characterized by typical low amplitude structure, large lateral variation of formation velocity and obvious low velocity anomaly. The above two features brought new challenges to the research of time-depth conversion method for this oilfield. Based on the flaw and insufficiency of conventional velocity modeling method, this paper proposed a new method that firstly determines the distribution range of low velocity anomaly by seismic data combined with logging and geological stratification, then creates seed points inside the anomaly range according to the degree of velocity anomaly, finally builds the velocity field by spatial interpolation under the restraint of velocity at seed points and well points. The velocity field can finally be used for time depth conversion. From actual drilling situation, this method can improve the prediction accuracy more greatly than conventional methods and has made a good practical application.

New method for productivity study of horizontal well after water breakthrough in low permeability water flooding reservoir

YUAN Lin, LIXiaoping, LI Songcen

2015, Vol.27(3): 127–132 Abstract ( 485 ) PDF (667 KB) ( 549 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.03.020

During the development of low permeability water flooding reservoir with horizontal well, water breakthrough is an important factor to restrict the production. Based on the Joshi theory of productivity of horizontal well, this paper simplified 3D flow of horizontal well into two 2D flows; considering the startup pressure gradient, used conformal mapping method to obtain productivity formulas in two 2D flow planes respectively; combined with the flow characteristics of oil-water two phase during non-piston-like displacement in water flooding reservoir, eventually obtained a new production formula of horizontal well in low-permeability water flooding reservoir. Through case study and comparison, the results calculated by new formula and single-phase productivity formula of horizontal well are more than the actual output, but the result calculated by new formula has a small relative error with actual output, only of 2.94%. It demonstrates that the new formula has a high degree of accuracy and is very practical. The study will provide a new method for predicting the production after water breakthrough of horizontal well in low permeability water flooding reservoir.