Lithologic Reservoirs

The advantages of huge carbonate reservoirs in Riphean period （1 650～800Ma） and Wendian period （670～ 590 Ma） of East Siberian platform include the following aspects: the formation of high quality source rock of dark shale during the Riphean Aulacogen evolution stage, the long-term developed paleo-uplifts within the craton basins are the major oil and gas enrichment zones, the stable distributed cap rock of gypsum is the key for the preservation of ancient reservoirs and the lithologic reservoir with structural background is the main reservoir type for petroleum accumulation. Comparing with the Sichuan, Tarim and Ordos basins in China, the common features of carbonate reservoir in these basins include strong heterogeneity and rapid lateral alternation. The differences include the significant changing of hydrocarbon generation indicators of shale source rock, the large thickness of Mesozoic to Cenozoic sedimentation and the deep burial of the lower combination within the superimposed basins. The carbonate exploration in China should comprehensively focus on the following aspects: evaluate the shale source rock of Sinian and Cambrian, evaluate the cap-rock condition of multi-phase reconstruction superimposed basin and enhance the exploration of lithology reservoir with structural background. The recent exploration should focus on great basins, seek the great structural background and develop the great combination zones of structure and lithology. Focusing on Sichuan, Tarim and Ordos basins, we should carry out structural reservoirs exploration of large-scale uplifts and buried hills and stratigraphy and lithologic reservoirs exploration of regional unconformity, slope zones of paleo-uplifts, great pinch-out zones of strata, reef on platform margin and grain banks symbiosis with evaporate rock within platform.

Influencing factors of reservoirs for Ordovician Majiagou Formation in the surrounding area of paleo-uplift in Ordos Basin

YANG Hua，WANG Baoqing，SUN Liuyi，LIU Baoxian，WANG Hongwei，MA Zhanrong

2013, Vol.25(3): 9–16 Abstract ( 566 ) PDF (1853 KB) ( 595 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.002

Based on the analysis of tectonic setting, petrology characteristics, biologic criteria and saline minerals, The Ordovician Majiagou Formation in the surrounding area of paleo-uplift in Ordos Basin deposited in a carbonate platform of restricted epeiric seas. The fifth member of Majiagou Formation deposited in gypsodolomite flat and gypsic saline lake where water cycle was restricted and salinity was high. The sedimentary environment of the fourth member of Majiagou Formation was relatively broad. Due to the compaction, porosity of the original carbonate sediments decreased greatly.The degrees of order for dolomite display low and changeable values. The dolomites are characterized by high δ18O values, Fe2+ contents and Sr87/Sr86 ratios, low Sr2+ and Na+ contents, and stable δ13C values comparing with original sedimentary values. The dolomites precipitated through microbial activity in the restricted environments with high salinity, and reformed by the karstification latter. The dissolution created different types of pores,caverns and fractures. The karstification formed karst geomorphic unites, such as karst highlands, karst platforms, eroded slopes and karst basins. The dolomitization and karstification are constructive processes, while compaction,cementation and dedolomitization are destructive processes. Abundant anhydrite nodules deposited in the anhydrite dolomite flats near anhydrite salt lakes,which is favorable for the creation of anhydrite nodule mold pores. The karstification developed well in karst eroded slopes, where abundant horizontal strata-bound dissolved pores and vugs were easily formed. In the transitional zones of slopes and basins, karstification was weak, while dedolomitization and cementation developed well. Because of the influence of sedimentation,diagenesis and karstification, the formation and evolution of the carbonate reservoirs are complicated.

Oil-gas source correlation in Dongping area, Qaidam Basin

CAO Zhenglin，WEI Zhifu，ZHANG Xiaojun，YAN Cunfeng，TIAN Guangrong，MA Feng

2013, Vol.25(3): 17–20 Abstract ( 672 ) PDF (1274 KB) ( 592 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.003

Using the biomarker parameters of n-alkane, the carbon isotope of full oil and the distribution pattern of single molecule, combined with the composition and carbon isotopic characteristics of natural gas, this paper discussed the oil and gas origin and genesis in Dongping area, Qaidam Basin. The results show that the n-alkane odd and even carbon number predominance of condensate oil in Dongping 1 well is equivalent （CPI =1.021, OEP =1.004）, showing the characteristic of high-mature crude oil. The Pr/Ph is 3.06, showing the pristane advantage. The carbon isotope of condensate oil（-31.25‰） is close to the carbon isotope of the Jurassic limnetic facies crude oil in the northern margin of Qaidam Basin, and the distribution characteristics of single molecule carbon isotope demonstrate the organic biological source of terrigenous higher plants. It is considered that the oil and gas in Dongping area are from Jurassic hydrocarbon source rocks, and the natural gas is a typical coal-type gas.

Petroleum geologic characteristics and exploration prospect in Rovuma Basin, East Africa

KONG Xiangyu

2013, Vol.25(3): 21–27 Abstract ( 741 ) PDF (1230 KB) ( 774 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.004

In recently years, several giant natural gas fields have been found in East Africa, which makes Mozambique and Tanzania in East Africa become the focus of the gas generation in the whole world. According to new foreign statistical data, it is believed that the gas in East Africa are all from a same basin-Rovuma Basin. Rovuma Basin is one of the few unexplored Tertiary delta sedimentary basins in the world. Recent natural gas exploration findings confirm that the basin has huge resource potential and favorable exploration prospect, but the exploration degree is low, and the knowledge of natural gas generation and accumulation is still at the primary stage. It is supposed that there are four set of source rocks, the gas is mainly of thermogenic gas in Mesozoic strata, and Paleogene biogenic gas may also exist. The main reservoirs are delta sand bodies in Paleocene, Eocene and Oligocene of Paleogene and Miocene of Neogene. The potential reservoirs include Permian-Triassic clastic rocks, Upper-Middle Jurassic clastic rocks and carbonate rocks and Cretaceous clastic rocks and carbonate rocks. In the background of global transgression, Upper Cretaceous shale is regional cap rock, Paleogene and Neogene layer shale is local cap rock, and during Jurassic and Cretaceous, shale can act as potential cap rock in the sedimentary environment of restricted sea. Rovuma Basin is a composite basin of lower rift deposit and upper delta sediment, which has excellent hydrocarbon accumulation condition. The study of Rovuma Basin will be in favor of guiding the international corporation in east Africa, and help the decision of oversea energy strategic target.

Diagenesis and its quantitative evaluation of the second member of Kongdian Formation in Cangdong Sag, Huanghua Depression

LIAO Ran

2013, Vol.25(3): 28–35 Abstract ( 562 ) PDF (2077 KB) ( 648 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.005

Based on systematic observation of normal and cast thin section, scanning electronic microscope, cathodoluminescene and analysis of X-ray, the characteristics of main diagenesis of the second member of Kongdian Formation in Cangdong Sag were analyzed. The result shows that it is of medium-strong compaction, medium cementation and strong dissolution in Nanpi slope, where clay coats can restrain the quartz enlargement and protect the primary and secondary dissolved pores. Shenvsi fault-nose is characterized by medium compaction, low cementation and strong dissolution. Kongdian tectonic zone is characterized by low compaction, medium cementation and low dissolution. The quantitative analysis of diagenesis shows that compaction, cementation and dissolution can cause -26.1%, -4.3% and 6.0% of porosity fluctuations respectively, and dissolution is important constructive diagenesis.

Sedimentary facies of Shahejie Formation in Jinzhou 20-2 Gas Field in Liaodong Bay

NAN Shan， HAN Xuefang， PAN Lingli， WANG Yuxiu， LIU Zhigang

2013, Vol.25(3): 36–42 Abstract ( 569 ) PDF (1479 KB) ( 716 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.006

The reservoir of the upper of the second member of Paleogene Shahejie Formation in Jinzhou 20-2 Gas Field in Liaoxi low uplift has the characteristics of complex lithologies, deep buried depth, thin thickness and great lateral variations. The reservoir distribution is an important restriction factor for the development adjustment of the gas field. Based on petrography, this paper studied sedimentary microfacies and environment from the data of core observation and thin section identification, together with the well logging curve morphological feature and lithofacies assemblage pattern, and recognized four kinds of microfacies including organic bank, carbonate restricted platform, clastic bank and deep lake. Sedimentation landform of target formation in the study area was restored by application of seismic horizon flattening technique. Based on the division result of single well facies, the plane microfacies distribution of the upper of the second member of Shahejie Formation was analyzed combined with analysis of sedimentary environment and understanding of ancient landform restoration. It is suggested that sedimentary microfacies of the upper of the second member of Paleogene Shahejie Formation in Jinzhou 20-2 Gas Field is lake-island type sedimentation, and it is obviously controlled by ancient terrain. The reservoir lithology consists of carbonate rock, sandstone and peperite. Thus,relatively speaking, bioclastic carbonate is with the best reservoir properties and thick layer. Reservoir development and distribution are controlled by sedimentary microfacies.

Formation and evolution of the reef flat facies lithologic gas reservoir of Changxing Formation in Yuanba Gas Field, Sichuan Basin

DUAN Jinbao， LI Pingping， CHEN Dan， FENG Chong

2013, Vol.25(3): 43–47 Abstract ( 419 ) PDF (1540 KB) ( 592 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.007

The origin, source and evolution of the reef flat facies lithologic gas reservoir of Changxing Formation in Yuanba Gas Field were studied systematically by themethods of geologic and geochemical inversion. The result shows that the gas of the reel flat facies lithologic gas reservoir is mainly from the oil cracked gas of paleo-reservoir, and a small part of the gas is directly from the source rock of Upper Permian. During Late Triassic-Early Jurassic, crude oil migrated to reservoir along the interlayer fractures and joint fissures, and formed paleo-reservoir. During Late Jurassic-Late Cretaceous, the paleoreservoir cracked, gas migrated along fractures and pore reservoir and accumulated, and formed paleo-gas reservoir. Since Late Cretaceous, gas further migrated and formed the present gas reservoir. The gas reservoir experienced physical adjustment and chemical alteration of natural gas component. Small amplitude of uplift in the northwestern Yuanba Gas Field leads to the relatively shallow burial depth and the weak TSR response.

Diagenetic reservoir facies classification and log response features in GY Oilfield

LI Miao，PU Chunsheng，JING Cheng，YANG Hongbin，HE Yufei

2013, Vol.25(3): 48–52 Abstract ( 552 ) PDF (1038 KB) ( 444 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.008

The extra-low permeability reservoir of Chang 6 and Chang 4+5 reservoir in GY Oilfield has the characteristics of intense compaction and cementation, complicated diagenesis and diagenetic process. Based on the analysis of the lithology and physical properties, pore evolution, pore types and pore structure features, this paper classified the diagenetic reservoir facies into four kinds in this area, and determined the log response features of each kind of diagenetic reservoir facies. This paper also analyzed the log response features diversity of different diagenetic reservoir facies in extra-low permeability reservoir by case analysis, and classified diagenetic reservoir facies effectively which can provide effective guidance for screening the oil-bearing zones and further efficient development.

Approaches and prospects of provenance system analysis in sedimentary basins

WEI Ran，LI Hongyang，YU Bin，CAI Laixing，WANG Qilong

2013, Vol.25(3): 53–57 Abstract ( 897 ) PDF (752 KB) ( 1190 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.009

Provenance analysis is one of the most important aspects in the research of sedimentary basins, and it is of great significance in studying the relationship and the interaction between basins and hills. At present, lots of experts put forward many kinds of analytic procedure, but they cannot constitute a system. This paper summarized the study ways from four aspects: the determination of source area, the analysis of parent rock features in the source area, the determination of moving path and the tectonic setting of source area, and established a frame of approaches about provenance system. In different sedimentary basins, according to the abundance of geological data, qualitative analysis and quantitative analysis should be combined and many kinds of study ways should be made up for each other. Only in this way, the conclusion of the characteristics of provenance system would be scientific and reasonable.

Sedimentary system and reservoir characteristics of Lower-Middle Triassic in Beisantai swell, Junggar Basin

SHAO Guoliang， DU Shekuan， TANG Xianglu， ZHAO Guangliang，DAI Long， ZHANG Daquan

2013, Vol.25(3): 58–65 Abstract ( 597 ) PDF (1808 KB) ( 563 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.010

Based on the regional geologic settings, combined with the analysis of sedimentary sequence, core features and well logging data, this paper studied the sedimentary system, evolutionary process and reservoir characteristics of Beisantai swell, and predicted the favorable range zone. The result shows that from the northeast to southwest of the study area, there successively developed braided delta front subfacies，delta front subfacies and shallow lake subfacies, and the principal source is mainly from the Kelameili mountain in the northeast. The main controlling factors of the sedimentary facies distribution are tectonic uplift and subsidence, lake level changes and sediment supply. According to the reservoir physical properties, the study area belongs to low permeability and low porosity type Ⅲ reservoir, and high quality reservoir facies belts are mainly developed in underwater distributary channel.

Study on resource potential of shale oil in A-29 Block, North America

ZHU Yanhe， HU Qianze， CHEN Guihua， CHEN Xiaozhi

2013, Vol.25(3): 66–70 Abstract ( 539 ) PDF (1380 KB) ( 625 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.011

Shale oil play is continuous petroleum accumulations just like shale gas, both of them are unconventional resources. The A-29 block locates in north of favorable prospecting area of Tuscaloosa Marine Shale（TMS）, which is one of the best shale oil potential areas in North America. Because of being lack of geologic awareness, the resources potential is not clear, the next step of exploration is hard to deepen. Now, knowing the resources potential and selecting favorable area are very important for next exploration and development. Analyses of lithologic association of TMS formation indicate that upper layer and lower layer are tight rock, and middle rock is shale oil reservoir. OOIP is calculated by volumetric method and the range is from 0.30×108 m3 to 2.56×108 m3,and resources abundance is from 7.36×104 m3/km2 to 63.22× 104 m3/km2. Based on research of some key geologic parameters which are depth, thickness, TOC, Ro and brittleness, the results show that A-29 block is a good shale oil exploration area, TMS formation is so hard for hydraulic fracturing, and the shale oil favorable area is in southeast of block. But the exploration risk is in existence, the lower layer of TMS is tight sand and tight limestone which contains free water. Once the process of fracture stimulation is not proper and length of fracture is not controlled, the breakthrough will happen. So, high risk of completion should be noticed.

Study on micro-pore structure characteristics of Chang 8 reservoir in Yingwang Oilfield, Ordos Basin

ZHANG Yiguo，SUN Wei，REN Dazhong，WANG Yue，QI Hengxuan，QU Xuefeng

2013, Vol.25(3): 71–76 Abstract ( 578 ) PDF (1288 KB) ( 470 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.012

Chang 8 reservoir in Yingwang Oilfield is characterized by strong heterogeneity, complex micro-pore structure and low yield. Based on scanning electronic microscope, casting thin slice, high pressure mercury penetration and oil/water displacement experiment, this paper studied the petrology characteristics, physical properties, micro-pore structure and its effect on flowing ability and oil displacement efficiency of Chang 8 reservoir in Yingwang Oilfield. The result shows that the pore structure can be divided into three types, including residual intergranular pore-dissolved pore, dissolved pore-residual intergranular pore and micropore-dissolved pore. We should focus on the dissolved pore-residual intergranular pore which is the best reservoir in the study area. The type and relative content of fillings, the core porosity and pore throat radius are the main factors influencing the flowing ability for low permeability reservoirs.

Diagenesis and its effect on reservoir properties of Chang 2 oil reservoir set in Longzuigou area of Xiasiwan, Ordos Basin

LI Delu， ZHAO Weiwei

2013, Vol.25(3): 77–81 Abstract ( 454 ) PDF (1286 KB) ( 511 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.013

Based on analysis of cast sections, X-ray diffraction, vitrinite reflectance, scanning electronic microscope and cathodoluminescence, this paper analyzed and evaluated the characteristics of petrology, reservoir physical properties, diagenesis, diagenetic stage and reservoir microstructure of the Chang 2 oil reservoir bet in Longzuigou area of Xiasiwan in Ordos basin. The results show that the Chang 2 oil reservoir set mainly developed medium and fine-grained lithic arkose. Its pore type is mainly intergranular pore and the main throat type is dominated by punctate throat. The diagenesis types are mainly compaction, cementation, replacement and dissolution. The compaction has the most destructive effect on reservoir physical properties in the process of porosity evolution, followed by cementation and replacement, while dissolution improves the reservoir pore significantly. Combined the analysis data of the fluid inclusion and the vitrinite reflectance, it is considered that the Chang 2 oil reservoir set in Longzuigou area is now in the middle diagenetic stage A.

Colored deconvolution of mixed phase wavelet

WANG Wanli， LI Guofa， GUI Jinyong

2013, Vol.25(3): 82–86 Abstract ( 493 ) PDF (1109 KB) ( 782 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.014

The conventional seismic data process methods for high resolution assume that reflection coefficient series are accordant with Gaussian Gauss White Noise. Through the statistical analysis of reflection coefficients obtained from the actual logging data, it is concluded that the reflection coefficients are non-Gaussian distribution and their spectrums tend to blue, which can be applied to extract mixed phase wavelet and carry out deconvolution. Based on systematic analysis of the method of high order cumulant mixed phase wavelet extraction, and in order to avoid the influence of phase winding and accumulated error on phase estimation accuracy, the method of multi path average bispectrum was proposed. The actual seismic data processing result shows that this method can improve the resolution of seismic records effectively and enhance its ability of detecting thin layer.

Application of “two layer and six terminal element” shale evaluation method in Lower Yangtze area

HUO Fengbin， ZHANG Tao， XU Fa， LU Jinsong

2013, Vol.25(3): 87–81 Abstract ( 559 ) PDF (1118 KB) ( 512 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.015

The evaluation and optimization of the target layer of shale gas are the emphases in the early stage of research of shale gas exploration. Shale is not only the hydrocarbon source bed but also reservoir. A set of technical method which can be used to accurately and rapidly evaluate shale is the key of the research. Through the practice of shale gas exploration study in Lower Yangtze area,“two layer and six terminal element” shale evaluation method was proposed. By optimizing parameters that can reflect shale hydrocarbon generation potential and reservoir performance, we drawn up quantitative evaluation criterion of all parameters, then used “two layer and six terminal element” diagram to diagrammatize, classify and evaluate shale semiquantitatively. The method has great systematization and operability. This method was applied to comprehensively evaluate four sets of Paleozoic shale developed in the west of Lower Yangtze area. Lower Permian Gufeng Formation and Upper Permian Dalong Formation have good hydrocarbon source condition and reservoir properties of shale, and these two formations are the main target layers for the shale gas exploration.

Review on time-frequency analysis technique and its application in seismic exploration

PANG Rui， LIU Baihong， SUN Chenglong

2013, Vol.25(3): 92–96 Abstract ( 718 ) PDF (1868 KB) ( 984 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.016

Spectral decomposition techniques can be used to extract some useful information in time-frequency domain which can not be found in conventional time domain, and improve the prediction ability of thin reservoir and lithologic traps. The key point of spectral decomposition is time-frequency analysis. This paper expounded the principle and method of time-frequency analysis technique and its significance to seismic data processing. Some application cases of time-frequency analysis technique in seismic exploration were presented to illustrate the progress of the application of time-frequency analysis in seismic exploration, including spectral decomposition, spectral inversion, waveform classification and frequency splitting processing. From the process we can see that the application of time-frequency analysis technique in seismic exploration has a fine prospect.

Influence of moisture content in coal rock on permeability

MA Feiying，WANG Yongqing，WANG Lin，ZHANG Shuanglong，ZHANG Qiang

2013, Vol.25(3): 97–101 Abstract ( 583 ) PDF (852 KB) ( 612 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.017

In order to explore the influence of moisture content in coal rock on permeability, this paper made experiments on raw coal samples in a northern coal-bed methane blocks of No. 3 and No. 15 coal bed. The results show that: under the same conditions, the permeability of three kinds of coal rock of dried coal samples, 3% moisture content coal samples and 6% moisture content coal samples first decreases and then increases with the increase of pore pressure, roughly displays “parabola” change. The permeability of dried coal samples is significantly higher than that of moisture content coal samples. With the increase of moisture content, permeability of coal samples decreased. On the basis of experiments and previous studies, using comparative analysis method on experimental data of the coal samples with different moisture content, we modified the Langmuir isothermal equation and set up a permeability model considering the moisture content and coal rock contraction-expansion. Finally, contrastively analyzed the predicted results by model and site well testing permeability data of the application examples, and relative error is small, so this model has certain guiding significance for coal-bed methane mining.

Evaluation of glutenite heavy oil reservoir based on multi-mineral log interpretation method

XIE Weibiao，YIN Qiuli，LIU Diren，YUAN Jihuang, CHEN Jian

2013, Vol.25(3): 102–105 Abstract ( 564 ) PDF (1148 KB) ( 395 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.018

The log interpretation for glutenite heavy oil reservoir is difficult because of its complexity of porosity and permeability and its special fluid property. Multi-mineral log interpretation method can effectively utilize all kinds of logging information to get reservoir parameters accurately. The reservoir JMSR area is mainly of glutenite with complex mineral composition. By using multi-mineral model optimization method, we obtained the porosity and mineral composition content and computed the permeability with Scheidger formula, and the results are in accord with the actual core data. The multi-mineral log interpretation method can be used to recognize heavy oil reservoirs by computing mud invade depth, can increase interpretation coincidence rate and provide dependable data for exploitation in JMSR area.

Genetic mechanism and identification methods of Chang 6 low resistivity reservoir in Zhidan and Ansai area, Ordos Basin

XIE Qing， WANG Jianmin

2013, Vol.25(3): 106–111 Abstract ( 568 ) PDF (1416 KB) ( 535 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.019

Low resistivity reservoirs developed well in Mesozoic Yanchang Formation in norhtern Shanxi, with wide distribution and tremendous resource potential. But because of its complex genetic mechanism and diversified forms, the traditional method is difficult to identify them. Combining with the actual oilfield production practice, according to logging, well logging, experimental analysis and production test, with the main producing oil group as the research object, based on the comprehensive geological research, this paper studied the genetic mechanism of Chang 6 low resistivity reservoir in Zhidan and Ansai area, and discussed its identification methods. The results show that complex pore structure, clay with conductive ability and high water salinity are the main causes for Chang 6 low resistivity reservoir, and the methods of crossplot, logging curve overlapping and adjacent water layer can be used to improve the recognition accuracy of the low resistivity reservoir in the study area.

Relationship between sedimentary facies and remaining oil distribution of Karamay Formation in eastern block 1 of Karamay Oilfield

ZHU Zhiliang， XIONG Di， YUE Yuanzhou， LU Xiaowei

2013, Vol.25(3): 112–118 Abstract ( 605 ) PDF (1391 KB) ( 692 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.020

Karamay Formation in eastern block 1 of Karamay Oilfield is rich in remaining oil, but the distribution of remaining oil is very complicated, with the characteristics of highly dispersed and local enrichment. Sedimentary facies are one of the main factors controlling the reservoir development, so the fine description of sedimentary facies can provide help for studying the regulation of the remaining oil distribution. Based on core and well logging data, the characteristics of petrology, sedimentary structure and electroficies were studied. Trough the analysis of facies association, facies matching and well logging response, the sedimentary facies types of Karamay Formation in eastern block 1 were identified, including alluvial fan, braided river, fan delta and lake facies. The plane distribution and vertical evolution of sedimentary facies were discussed. It is considered that Karamay Formation mainly experienced twice of lake transgression, and can be vertically divided into three up fine normal cycle. The remaining oil distribution in the microfacies that have poor properties was discussed, which has important guiding significance for the further development of the oilfield.

1. Research Institute of Petroleum Exploration and Development， Tianjin Branch of CNOOC， Tianjin 300452， China； 2. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation， Southwest Petroleum University， Chengdu 610500， China

WANG Dawei， LI Xiaoping

2013, Vol.25(3): 119–122 Abstract ( 903 ) PDF (896 KB) ( 546 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.021

In general case, the actual finishing drilling horizontal well is not absolutely horizontal, the well trajectory is undulant as wave. When the wellbore bending degree is big, gravitational potential energy causes the bigger difference of inflow performance than the ideal horizontal wells. Therefore, it is necessary to do in-depth analysis of the horizontal well inflow performance. The horizontal well with curved trajectory was approximately regarded as a continuous structure which is composed of a series of slant wells. By using the reservoir-wellbore flow coupling semi-analytical model, this paper studied the effects of well trajectory bending on horizontal well inflow performance, and compared the calculation results with the multi-branch horizontal wells. The result shows that well trajectory bending will affect the productivity of horizontal wells and wellbore pressure distribution, the radial inflow curves of horizontal wells and multi-branch horizontal wells have a big difference with ideal situation, and the shape fluctuates with well trajectory changes.

Applying vector well pattern to optimize the flooding well site of small reservoir

NIE Haifeng， TAN Bei， XIE Shuang， HE Yuanyuan

2013, Vol.25(3): 123–125 Abstract ( 517 ) PDF (896 KB) ( 555 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.022

The DX 12 well field is characterized by relatively small sand bodies, low reserves abundance and has the characteristic of “one sand, one reservoir”. The method of scattered water flooding is applied to develop the nonoverlapping regions of the reservoir. This paper established a reservoir physical simulation system of five-spot water flooding pattern, verified the effectiveness and practicality about vector well pattern in the development of heterogeneous reservoir, and applied the theory of vector well pattern combined with the method of numerical simulation to optimize the scattered well pattern of non-overlapping regions of the small reservoir in DX 12 well field. The result shows that the optimization of well pattern has a significant effect on improving the development effect and enhancing the producible oil index.

Operation parameters optimization of steam flooding with the combination of vertical and horizontal wells

TIAN Hongzhao，SUN Ye

2013, Vol.25(3): 127–130 Abstract ( 555 ) PDF (1021 KB) ( 566 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2013.03.023

The S block is a low-middle porosity and low-middle permeability reservoir. This paper studied the operation parameters for steam flooding with the combination of vertical and horizontal wells by numerical simulation. The result shows that the optimum operation parameters are as following: the vertical distance is 15 m between the vertical well and horizontal well, and the vertical distance is 7 m between the horizontal well and reservoir bottom; after eight cycles of vertical well and six cycles of horizontal well, formation pressure dropped down to 5 MPa; the best steam injection rate is 84 m3/d, downhole steam dryness is greater than 40%, and production-injection ratio is 1.2. These optimum operation parameters make the steam flooding effective in S block, enhance the oil recovery factor, also provide reliable theoretical basis of operation parameters for steam flooding with the combination of vertical and horizontal wells in other similar reservoirs, and have very good reference significance.