Lithologic Reservoirs

Oil and gas production from reservoirs is the result of drive of reservoir energy. Reservoir energy evaluation is a routine job during exploitation of reservoirs. Conventional evaluation parameters of reservoir energy are the dimensionless elastic production ratio and the pressure drop per recovery of reservoir reserve. However, the two evaluation parameters both give out logically inverse results, i.e. the reservoir energy is increasing with the depletion of reservoirs. In order to evaluate reservoir energy scientifically, this paper proposed energy index method, which is the ratio of reservoir pressure to limit bottom pressure of production wells. The new method is closely related to the lift style of wells, and can properly evaluate the reservoir energy status with the reservoir energy decreasing while depletion. The application result shows that the energy index is easier and more practical to use than the conventional method.

A new method for determining physical property lower limit of tight sandstone reservoir and reservoir system classification

ZHANG Anda， WANG Cheng， QIAO Rui

2014, Vol.26(5): 5–8 Abstract ( 638 ) PDF (403 KB) ( 875 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.002

Tight sandstone reservoir of Fuyu oil layer is a new target of current exploration and development, but there lacks clear definition of the property lower limit.By using statistical method combining physical properties with reservoir productivity, this paper carried out statistical analysis of physical properties respectively on the commercial oil layer and low yield oil layer according to the cumulative probability loss 10%. The physical property lower limit of commercial reservoir is φ=7.1%，K=0.08 mD. The physical property lower limit of low yield oil layer is φ=5.6%, K= 0.0047 mD. Based on function fitting method combining tight sandstone critical pore throat radius with mercury injection data, it is determined that the physical property lower limit is φ=4.46%, K=0.041mD. Considering the lower limit value being close to the lower limit of low yield oil layer, we took the lower limit value as the physical property lower limit of tight reservoir. Based on the physical property lower limit of the tight and commercial reservoir and the conventional reservoir classification boundaries, we classified sandstone reservoir system into class Ⅲ, class Ⅱ and class Ⅰ of tight reservoir, and low, middle, high and extra-high porosity and permeability reservoir. The determination of tight reservoir physical property lower limit and reservoir system classification can provide important parameters and technical supports for productivity calculation and evaluation of tight reservoir.

Spatial matching relation between source rock and caprock and its control action on oil-gas accumulation in Fangzheng fault depression

FU Guang， L IU Tongxi， SHI Jijian， L I Y unfei， Y ANG Lifeng

2014, Vol.26(5): 9–14 Abstract ( 437 ) PDF (656 KB) ( 437 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.003

In order to study oil-gas accumulation law in Fangzheng fault depression, based on the characteristics of development and distribution of source rock and caprock, this paper studied the spatial matching relation between source rock and caprock and its control action on oil-gas accumulation in Fangzheng fault depression. The result shows that there are two types of spatial matching relation between source rock and caprock itself and lower sourcerock and upper caprock in Fangzheng fault depression. There are two sets of spatial matching relation between source rock and caprock in the first type, and they formed in Xin’ancun-Wuyun Formation. There are three sets of spatial matching relation between source rock and caprock in the second type, and they formed in Xin’ancun-Wuyun Formation to the second member of Baoquanling Formation. The first and third sets distributed in the whole fault depression, the second and fifth sets only distributed in the eastern fault depression, and the fourth set only distributed in the western fault depression. The control action of these five sets of spatial matching relation between source rock and caprock on oil-gas accumulation mainly displays in the following three aspects: ①the numbers of spatial matching relation between source rock and caprock control oil-gas accumulation and distribution horizons; ②the numbers of spatial matching relation between source rock and caprock in the same horizon control oil-gas accumulation amount; ③caprock quality in spatial matching relation between source rock and caprock also controls oil-gas accumulation amount.

Quantitative simulation on pore evolution in diagenetic process of sandstone: A case study from Chang₈ oil reservoir set in Ansai area, Ordos Basin

LIAO Peng，TANG Jun，WANG Kai，YANG Xipu，WANG Qi

2014, Vol.26(5): 15–22 Abstract ( 778 ) PDF (851 KB) ( 771 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.004

The change of porosity in buried diagenetic process is a continuous process, which has important significance to hydrocarbon accumulation and regional reservoir evaluation. By using mathematical statistics and numerical simulation method, this paper carried out quantitative simulation of pore evolution during the whole burial diagenetic process of Chang 8 oil reservoir set in Ansai area. Based on analysis of petrologic characteristics, diagenetic features, burial history and diagenesis history, with current porosity as boundary constraint conditions, geological time and burial depth as variables, the whole pore evolution of Chang 8 oil reservoir set from initial burial until nowadays was divided into two independent processes: porosity decrease and porosity increase, for which two mathematical models were established respectively. The quantitative simulation result indicates that the porosity decrease model of mechanical compaction stage is a continuous function with burial depth as the independent variable, while that of ompactioncementation stages and porosity increase model under temperature window conditions and secondary porosity preservation （65～100 ℃） are continuous functions with geological time and burial depth as the variables. The whole pore evolution quantitative simulation built from the superimposition of porosity decrease and increase is a piecewise function with four sections. Finally, through the exemplification, it is verified that this approach works well in sandstone pore evolution simulation.

Influencing factors of Carboniferous volcanic reservoir in Ludong-Wucaiwan area, Junggar Basin

LIU Shuangquan，CAO Yuanting，ZHAO Guangliang，ZHU Jun，SHI Ji’an，ZHANG Shuncun

2014, Vol.26(5): 23–29 Abstract ( 1487 ) PDF (924 KB) ( 619 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.005

By use of the geochemical parameters of hydrocarbon source rocks, reservoir properties and drilling data, this paper analyzed the hydrocarbon generation conditions, reservoir characteristics and evolution, hydrocarbon migration pattern and reservoir-caprock assemblage of Carboniferous volcanic reservoir in Ludong-Wucaiwan area. The result shows that there mainly developed two sets of hydrocarbon source rocks within the Dishuiquan Formation and Batamayi- neishan Formation in Ludong-Wucaiwan area, and the rocks have high organic matter maturity. The reservoirs possess the characteristic of good properties, strong heterogeneity and a greater physical properties difference between different types of reservoir. Faults and unconformity surfaces are the main hydrocarbon migration channel. As the oil and gas enter into the reservoir along these channels, they formed four reservoir-caprock assemblages: dacitetuff, volcanic breccias-tuff, basalt-mudstone and granite-mudstone. Oil and gas reservoirs mainly enrich in the weathering crust reservoir which is close to the top of the Carboniferous.

Study on genetic type of micropore in shale reservoir

HE Jianhua，DING Wenlong，FU Jinglong，LI Ang，DAI Peng

2014, Vol.26(5): 30–35 Abstract ( 822 ) PDF (651 KB) ( 1230 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.006

By using field emission scanning electron microscope, this paper observed and described the size, shape, distribution and seepage characteristics of micropore in dark shale in northern and northwestern Guizhou. Based on the genesis, the pores were divided into three categories: primary sedimentary pores, secondary pores and mixed pores. Based on the development location, the pores were divided into ten sub-categories, such as intergranular pores, intra- crystalline pores, fossiliferous pores, organic matter pores and so on. The influencing factors for the pore development and the pore evolution characteristics of shale were discussed, which has important theoretical and practical significance forthestudyonshalereservoir.

Genetic mechanism analysis and prediction method of abnormal high pressure in Mahu slope area, Junggar Basin

QU Jianhua， WANG Zesheng， REN Benbing， BAI Yu， WANG Bin

2014, Vol.26(5): 36–39 Abstract ( 588 ) PDF (735 KB) ( 513 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.007

With the development of the oil and gas exploration, it is gradually recognized that the formation pressure has important effect on the hydrocarbon preservation and individual well deliverability. So it is necessary to quantitatively predict the formation pressure based on the seismic data. The prediction method of abnormal formation pressure widely applied now is based on the effective stress theory which is proposed by Terzaghi in 1923 and plays an important role in civil engineering practice. However, the effective stress theory has limitations in the porous medium which has complex structure. Considering the rock physical properties and mechanics equilibrium principle, we developed a new pressure prediction method based on the dual effective stress of porous medium through the introduction of dual effective stress equation related to porosity, making closer relationship among the overburden pressure, formation pressure and rock skelecton stress. We achieved good effect after putting this method in practical use to the formations in Mahu slope area, northwest of the Junggar Basin, through the analysis of the genesis of abnormal high pressure andconstrained by the geological origin.

Igneous reservoir identification technique in eastern sag of Liaohe

CHEN Xingzhou， TONG Hengmao， LI Bing， YANG Shuo

2014, Vol.26(5): 40–46 Abstract ( 627 ) PDF (1389 KB) ( 449 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.008

The igneous reservoir in eastern sag of Liaohe is characterized by complex geological environment and seismic reflection character, variable lithology and reservoir properties. The systematic research on structure features of igneous reservoir shows that igneous rocks are mainly controlled by Jiazhangshi-Jiexi slip faults system, symmetrically distributed fromsouth to north along the major fault, and mainly developed multicycle extrusive igneous rock and layered intrusive igneous rock. We used techniques of igneous rock seismic reflection identification, impedance inversion and time slice to identify Hongxing extrusive igneous body and Yulou intrusive igneous body, applied techniques of cycle classification, waveform clustering attributes and favorable reservoir inversion of igneous rocks to predict facies belt and favorable reservoir distribution of igneous bodies, and finally formed a set of identification and evaluation technique series of igneous rock. This set of technique series guided the exploration of igneous bodies in eastern sag of Liaohe and Lujiabao Sag, and it also provides technical support for igneous reservoir exploration in other area.

Diagenesis and its influence on reservoirs of Pliocene in a block of Moattama Bay Basin

WANG Yingchao， WANG Qiang， SUN Zuoxing

2014, Vol.26(5): 47–50 Abstract ( 687 ) PDF (683 KB) ( 547 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.009

The Moattama Bay Basin is located in the back-arc strike slip and extensional tectonic position with oil and gas enrichment, seeking favorable reservoirs become the key for the breakthrough of petroleum exploration in this area. By using techniques of casting thin section and X-diffraction, this paper analyzed mineral characteristics and diagenesis of Pliocene sandstone reservoirs in a block of Moattama Bay Basin. It is believed that the rock types of sandstone reservoir are mainly feldspar quartz sandstone and lithic quartz sandstone, with moderate maturity mostly. As a whole, the study area experienced diagenesis of compaction, cementation and dissolution, which influenced reservoir properties little. In the south of the study area, compaction is a main factor influences the reservoir properties dominantly. Destructive diagenesis has little effect on the porosity loss, so Pliocene formations possess advantages of forming hydrocarbonbearing reservoirs in this area.

Influence of diagenesis on reservoir properties in northern Ordos Basin

ZHAO Xiaohui，CHEN Juanping，QI Yaling，CAO Qing

2014, Vol.26(5): 51–56 Abstract ( 570 ) PDF (984 KB) ( 428 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.010

Based on analysis of conventional thin section, casting thin section, scanning electron microscope, cathodeluminescence and X-ray, this paper studied the reservoir diagenesis and its influence on reservoir properties of He 8 member in northern Ordos Basin. The result shows that because of the influence of diagenetic material and energy, pore types in the western zone are different from the pore types in the eastern zone of northern Ordos Basin. There are mainly intergranular dissolved pores and lithic dissolved pores in the western zone, whereas lithic dissolved pores and intercrystalline pores in the eastern zone. Besides, diagenetic facies can be divided into four types, among which the combination of siliceous cement phase and calcium dissolved phase is the favorable one. Reservoir properties are influenced by diagenesis, which displays that the cementation tighten reservoir and dissolution improved reservoir properties. Further research on reservoir diagenesis can provide theoretical foundation for the optimization of abundant gas accumulation zone and promotion of gas reservoir exploration and production in the northern Ordos Basin

Sedimentary microfacies of the fourth member of Quantou Formation in Fuyu Oilfield, southern Songliao Basin

CAI Dongmei

2014, Vol.26(5): 57–63 Abstract ( 522 ) PDF (936 KB) ( 474 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.011

Based on core and logging data, this paper systemically studied the distribution of sedimentary microfacies and sedimentary model of the fourth member of Quantou Formation in Fuyu Oilfield of southern Songliao Basin through analyzing the rock type, color of mudstone, grain size and sedimentary structure. The result shows that the study area developed meandering river-delta plain, including two types of subfacies and 12 types of microfacies. According to the logging characteristics of different microfacies, classified the plane distribution features of microfacies, established sedimentary model of shallow water deltas, and analyzed the characteristics of sedimentary evolution. This study can provide a reliable base for potentials tapping of remaining oil in Fuyu Oilfield.

Characteristics of shale reservoir of the first member of Qingshankou Formation in northern Songliao Basin

LIU Bo， WANG Fan， RAN Qingchang， LI Mei， DAI Chunlei， WANG Meng

2014, Vol.26(5): 64–68 Abstract ( 519 ) PDF (767 KB) ( 587 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.012

The reservoir quality is the key factor for influencing the enrichment of shale oil and gas. Through core observation, thin section identification, scanning electronic microscope, isothermal adsorption and other means, this paper studied the petrology and reservoir characteristics of oil shale of the first member of Qingshankou Formation in northern Songliao Basin. The result shows that the rock types of reservoir include with silt mudstone, silty mudstone, lime mudstone and siltstone. The silty mudstone, lime mudstone and siltstone are with higher contents of fragile mineral, and developed various types of reservoir space which constitutes a complexes level and vertical fracture net-system. Intergranular dissolved pores are more developed in thinsiltstone layers or laminate, and their porosity can reach micron level. The reservoir of the first member of Qingshankou Formation belongs to ultra-low porosity and ultra-low permeability reservoir. The silty mudstone, lime mudstone andcarbonaceous siltstone have best reservoir properties.

Influence of pore structure on reservoir quality of low permeability sandstone reservoir: A case study from Chang 8 oil reservoir set in Jiyuan area, Ordos Basin

CAI Yue，XIONG Qi，LI Yong，DING Yingchao，XU Wenjie

2014, Vol.26(5): 69–74 Abstract ( 592 ) PDF (945 KB) ( 443 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.013

Based on conventional constant-pressure mercury injection, cast image, scanning electron microscopy and slice observation, combined with constant-speed mercury injection, this paper studied the microscopic pore structure and its influence on reservoir quality of Chang 8 low permeability sandstone reservoirs in Jiyuan area. The result shows that Chang 8 reservoirs developed various pore types and the pore structure can be divided into four categories. The average pore-throat radius, median pore-throat radius, sorting coefficient and maximum mercury saturation have a positive correlation with reservoir properties, have a negative correlation with structure coefficient, and have little correlation with average coefficient, skewness and mercury withdrawal efficiency. Constant-speed mercury injection test further shows that physical properties of Chang 8 low permeability reservoir have little correlation with pore parameters, and reservoir quality are mainly controlled by throat. In the process of low permeability reservoir development, we should protect the throat effectively to achieve better development effect.

Reasons of low yield of tight sandstone gas of He 8 member in eastern Ordos Basin

ZHAO Huitao，WANG Huaichang，LIU Jian，DING Xuefeng，LIU Yan

2014, Vol.26(5): 75–79 Abstract ( 516 ) PDF (842 KB) ( 386 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.014

The reservoir of Neopaleozoic He 8 member in eastern Ordos Basin is characterized by low porosity, low permeability and low single well production, which restricts the large-scale development and submit scale of reserves, so it is necessary to study the characteristics of tight sandstone reservoir in this area and analyze the reason for the low yield of single well. By using cast thin sections, petrophysical analysis, high-pressure mercury injection, constant-speed mercury injection, gas water relative permeability, nuclear magnetic resonance and stress sensitivity experiment technology, this paper studied the characteristics of tight sandstone reservoir and the reasons of low yield of He 8 member in eastern Ordos Basin, and compared with Sulige Gas Field. The results show that the reservoir of He 8 member in the study area has poor properties, low content of rigid component, high content of plastic component, small pore throat radius and low movable fluid saturation. Strong stress sensitivity, great water lock damage and low gas permeability are the geological causes for the low yield of single well in the formation conditions.

Petrological and geochemical characteristics of dolomite of Zhanjin Formation in Jiaomuchaka area, Qiangtang Basin

HU Junjie，LI Qi，WANG Shuangqing，SHEN Bin，CHEN Ruoyu，GE Dongsheng

2014, Vol.26(5): 80–85 Abstract ( 504 ) PDF (1058 KB) ( 592 )

Current studies on oil-gas geology in Qiangtang Basin mostly focused on Jurassic strata, and only a few researches about the Paleozoic. Based on the data of thin section analysis, x-ray diffraction, cathodeluminescence, element geochemistry and C-O isotope, this paper studied the petrological and geochemical characteristics of dolomite of Zhanjin Formation in Qiangzi 5 well in Jiaomuchaka area, and discussed its genesis. The result shows that fine crystalline dolomite and crystal powder dolomite mainly developed in tidal flats of limited carbonate platform. They are characterized by cloudy centers and clear rims, clitellum and residual-grain, and the metasomatism is obvious. They are characterized by low-middle δ13C positive value （2.7‰～4.4‰）, low-high δ18O negative value （-8.4‰～-2.8‰）. Most diagenetic temperature are below 44℃, which indicates that the temperature degree of dolomitization is low. Salinity ranges from 20.98‰ to 30.16‰, below the salinity of sea. The middle value of the order degree of dolomite, together with the low content of Mg/Ca, Fe, Mn, Sr, and REE distribution pattern reveal a characteristic of burialdolomitization. All evidences indicate that the dolomite of Zhanjin Formation mainly formed in an early shallow burial environment with low temperature, and there may be a fresh water injection during the diagenetic process.

Lithologic reservoir exploration and effect in the periphery of Banghu Syncline, Qianjiang Sag

ZHANG Shuishan，ZHANG Sanyuan，ZHOU Hongyan，YI X iaoqin

2014, Vol.26(5): 86–90 Abstract ( 485 ) PDF (1029 KB) ( 452 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.016

The Banghu Syncline in Qianjiang Sag with abundant oil and gas resources is a typical inland lake by salt deposit. It is the favorable area for lithologic reservoir exploration. Because of complex vertical lithology combination, quickly lateral change of sand bodies, impedance of reservoir and non reservoir laminated obviously, it is difficult to identify the reservoir just by seismic attribute analysis and post-stack acoustic impedance inversion. Through many years of research, this paper put forward facies controlled reservoir prediction technology with high-fidelity pre-stack migration seismic data as a foundation, and the pre-stack simultaneous inversion of density as the core, and discussed the key technologies in pre-stack simultaneous inversion of density such as shear wave velocity estimation, stacked angels division and fluid detection. Practice proved that these exploration techniques are feasible, and they could be effectively used to identify lithologic traps and have great application prospects.

Wave field separating numerical simulation of anisotropic elastic medium directional one-way wave

CHEN Keyang

2014, Vol.26(5): 91–96 Abstract ( 548 ) PDF (1132 KB) ( 844 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.017

In order to further improve the knowledge of elastic wave propagation law, this paper firstly applied the Poynting vector to the up-down-left-right way wave field separation numerical simulation of multi-wave and multi-component anisotropicmediumelasticwave equation. According to the Poynting vector wave field numerical characteristic, the seismic one way wave field was automatically recognized and separated during the elastic wave numerical simulation. Taking isotropic anisotropic elastic medium model, tilt layer model and Marmousi model as examples, we carried out the corresponding numerical simulation. The result shows that the presented method can be used to obtain correct and effective computational results, it can achieve the up-down-left-right way wave field separation in both the snapshots and the numerical records, and the computational method is simple and easy to accomplish with small computational cost. Therefore, it has important application value in practical data processing and interpretation of multi-wave and multi-component elastic wave.

Genesis of low resistivity oil layer and evaluation of water saturation of the first member of Zhujiang Formation in Wenchang area, Pearl River Mouth Basin

CHEN Rong，LI Kui，HE Shenglin，HU Xiangyang，LUO Wei

2014, Vol.26(5): 97–101 Abstract ( 569 ) PDF (855 KB) ( 609 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.018

The reservoir of the first member of Zhujiang Formation in Wenchang area of Pearl River Mouth Basin is characterized by high content of shale, and the difference of resistivity between oil layer and water layer is little. So it is difficult to identify the oil-bearing reservoir and water-bearing reservoir by well logging interpretation. Based on the analysis of reservoir lithology, imaging data of thin interbed and litho-electric experiment in various salinity conditions, this paper studied the impact of different factors on the formation resistivity. The results show that the main causes of low resistivity oil layer are fine lithology, high content of shale, high content of irreducible water saturation and middle formation water salinity. Based on the genesis of low resistivity, tri-water model was used to evaluate the water saturation of low resistivity oil layer in the study area. The calculation results are consistent with the sealed coring results.

Comprehensive treatment of gas channeling at the later stage of CO₂ flooding

CHEN Zuhua， TANG Yong， WANG Haimei， CHEN Yuhan

2014, Vol.26(5): 102–106 Abstract ( 652 ) PDF (916 KB) ( 729 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.019

It is difficult for the field to achieve the CO2 miscible flooding efficiency of indoor experiments which could reach more than 90%. Recovery factor is limited mainly by several aspects, namely, CO2 viscous fingering, gravity overlap and reservoir heterogeneity, which exert negative influence on CO2 sweep efficiency. On the other hand, gas channeling aggravates gradually and development conflicts intensify continuously at the later stage of production. This paper analyzed development effect of CO2 flooding, regarding layer series of development, injection-production structure, way of injection and injection profile, moreover, proposed technologies of strata subdivision, injection in the top, water alternating gas（WAG）, polymer profile control and CO2+foam flooding. Good response has been observed after the onsite implementation. Reservoir overall gas-oil ratio decreased from 2 733.1 m3/m3 to 63.84 m3/m3, and daily oil production increased from 30.72 t（before gas injection） to 81.68 t（after gas injection）. Generally, this anti-gas channeling comprehensive technology is of great significance for similar reservoir scenario design and gas channeling prevention.

Effect of edge water incursion on productivity of horizontal well

LI Xiaoping，YUAN Lin，LUO Cheng，LIU Bin，LIU Zhenping

2014, Vol.26(5): 107–112 Abstract ( 524 ) PDF (878 KB) ( 480 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.020

During the development of reservoir with edge water, even if the water didn’t break through at the bottom of the horizontal well, the edge water incursion still influences the productivity of horizontal well. Based on the three- dimensional seepage field model of horizontal well, this paper divided the three-dimensional seepage field into two two-dimensional seepage field which are called internal seepage field and external seepage field respectively, used the methods of transformation of coordinates and conformal mapping to obtain the productivity formulas of the two two-dimensional seepage field, eventually got the new productivity formula of horizontal well considering the edge water incursion according to the principle of equivalent filtration resistance. Practical example shows that result calculated by new formula has small absolute and relative error with actual output, which indicates that the new formula is of high accuracy and good practicability. Sensitivity analysis demonstrates that productivity of horizontal well in consideration of edge water incursion is lower than that with no consideration of edge water incursion. Meanwhile, as the increasing of edge water incursion distance, the productivity of horizontal well decreased to a great extent with short horizontal section, while if the horizontal well length is long enough, the effect can be neglected. This study can provide a new solution to predict the productivity of horizontal wells during edge water incursion.

Water cut rising rules and water control countermeasures of reservoir of Xishanyao Formation in Niuquanhu block

PAN Youjun，XU Ying，WU Mei’e，ZHANG Zhongjin

2014, Vol.26(5): 113–118 Abstract ( 503 ) PDF (1016 KB) ( 484 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.021

Too rapid rising of water cut in Niuquanhu block has seriously restricted the stable oil production. Based on relative permeability curves, model prediction, plate method, water drive curve method, this paper studied water cut rising rule, obtained the recovery of each block changes with water cut and the water cut forecasting model, and compared with the actual water cut rising, finally optimized suitable method for the prediction of water cut in each block. The water cut rising rule of single well was analyzed. According to water cut change characteristics, we divided water cut rising into 5 types, analyzed the development features and formation mechanism of each type of water cur rising, and proposed corresponding technical countermeasures, which provides references for the effective development in Niuquanhu block.

Deduction and application of trinomial equation for water producing gas well with abnormal pressure

HUANG Xiaohai，LI Xiaoping，YUAN Lin

2014, Vol.26(5): 119–123 Abstract ( 581 ) PDF (756 KB) ( 543 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.022

The gas reservoir with abnormal pressure is characterized by high pressure and large productivity, so, it is very important to evaluate the deliverability. Meanwhile, the water breakthrough often occurs in the gas well under certain unreasonable working systems, which reduces the productivity significantly. Thus, it is vital to confirm the reasonable working system on the base of accurate prediction of the productivity of gas well with abnormal pressure. Considering stress sensitivity, non-Darcy flow, pulsation effect and water producing of gas well, this paper deduced a trinomial equation for water producing gas well with abnormal pressure. On the basic of the multiple linear regression and intersection method, absolute open flow capacity was determined and the correctness of result was demonstrated by the case analysis. The effects of permeability sensitivity coefficient and water/gas mass ratio on the gas well productivity were quantitatively analyzed. Calculation results show that: the effect of permeability sensitivity coefficient on gas well productivity is greater than that of producing water; for the gas well with large productivity, the effect of pulsating flow on the absolute open flow of gas well should not be overlooked. This study has significance for the exploitation of abnormal pressure reservoir.

Study on the flow rate and pressure profile of horizontal well in heterogeneous gas reservoir with bottom water

YUAN Lin， LI Xiaoping， ZHANG Lu， LIU Bin， WANG Wenbin

2014, Vol.26(5): 124–128 Abstract ( 593 ) PDF (773 KB) ( 450 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.023

During the developing the heterogeneous gas reservoir with bottom water, the distribution of different permeability along the wellbore will be an important factor which influences the flow rate profile and pressure profile. Based on the theory of seepage flow of horizontal well in heterogeneous gas reservoir with bottom water, this paper used infinitesimal method to divide the heterogeneous formation into several homogeneous formations, established the coupling model between formation and wellbore,which considered the variable mass flow in the wellbore, and established the semi-analytic model of flow rate profile and pressure profile of horizontal well in gas reservoir with bottom water.Case study shows that the flow rate profile presents different fluctuation as the changing distribution of permeability along the wellbore, the larger the value of Khmax /Khmin is, the larger the fluctuation range will be, meanwhile during drilling, if wellbore has drilled many high permeability formations, the production of horizontal well will be higher; near the toe and heel of horizontal well, the distribution of permeability has no influence on pressure profile, while in the middle of the wellbore, the larger the number of high permeability formation is, the greater the pressure drop in the wellbore will be and vice versa; the pressure drop along the total wellbore is very smaller,just 10-4 MPa, so during well testing, thepressure gage should only put at the heeling of the wellbore.

Optimization of fracture parameters of horizontal well in low permeability reservoir

WANG Xinjie， TANG Hai， SHE Long， ZOU Guili， ZHOU Jubiao， LI Xiangzhu

2014, Vol.26(5): 129–132 Abstract ( 537 ) PDF (713 KB) ( 757 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.05.024

Fracturing of horizontal well is often applied to increase oil well productivity in low permeability reservoir, and reasonable design of fracturing parameters of horizontal well can give full play to the role of increasing productivity of the artificial fracture. This paper abstracted the corresponding geological model on the basis of reservoir geological characteristics and the present state of exploitation in M fault block in Jiangsu Oilfield, established fractured model of horizontal well considering start-up pressure gradient by using threshold pressure of Eclipse application software, and contrasted with the PEBI grid and block grid model of horizontal well. The result shows that compared with the start-up pressure gradient, the fracture shape has a relatively small influence on the simulation results. The optimal fracture interval is 90 m, the optimal fracture number is 6, and the optimal fracture half-length is 130 m. This study provides a eference for optimization of the fracture parameters of horizontal wel in Jiangsu Oilfield.