The description of a single sand body for remaining oil predictions is critical to the enhancement of oil recovery of an old oilfield. Taking the fluvial facies of the Xingbei Oilfield as an example, a single sand body can be divided into four cate- gories—“tabulated reservoir”, “untabulated reservoir”, “single channel sand body” and “abandoned channel”—using the reservoir architecture analysis method. The boundary surface of each type may be mud barriers or only an erosion surface, which was traced by careful anatomization of the single sand body. Then, a fine single sand body reservoir geological model was constructed using a combination of a determined modelling method and stochastic modelling method. The numerical simulation is executed using the constructed geological model to forecast the remaining oil distribution quantitatively. The results show that the remaining oil was distributed in the bottom parts of the abandoned channel, top part of the point bar, tabulated reservoir, and channel edges. The movements of the injection water were mainly controlled by the mud barrier and superimposed styles of single sand body, which determines the formation of the remaining oil. This research has important guidance for oilfield development in the late stage, whose reservoir is composed of single sand bodies. Keywords Reservoir architecture · Single sand body modelling · Remaining oil distribution · Numerical simulation Introduction water injection development, and there are good interlayer conditions between the different sand bodies, which can The concept of single sand body, a relatively independent effectively close and block the fluid spillover (Qiu 1990). sand body element with related geological genesis in its Traditional reservoir modelling, mainly based on well data development that reflects the sedimentary characteristics of and seismic data, predicts the distribution of single sand sand body, the characteristics of waterflooding development bodies between wells, which reveals the spatial superposi- and the distribution of remaining oil to an extent, has been tion patterns and distributing law of different single sand widely used (Miall 1985, 1988). Specifically, two conditions bodies (Zhou et al. 2010; Wu and Li 2007). However, in the are necessary: (1) an obvious link of sedimentary origin, the later stage of development, the remaining oil in single sand same source and the same water system in a single period is an important research object, especially in a reservoir with of sedimentary sand body period, or the same water sys- a thin interlayer and serious heterogeneity (Li et al. 2003; tem in a multi-stage sand body erosion superimposed sand Zhang et al. 2013). It is important to develop a method to body; and (2) independence in development and a separate quantitatively anatomize the single sand body and reveal seepage unit with connectivity in different stage sand bod- its control on the remaining oil (Zhao et al. 2016; Yue et al. ies of the single sand body (Hjellbakk 1997). The effective 2008). This paper uses the Xingbei Oilfield as the research transmission of pressure can be realized in the process of object to propose a workflow for single sand body anatomi- zation and numerical simulation to forecast the distribution of remaining oil, which can lead to a further solution for the * Yin Yanshu enhancement of oil recovery. firstname.lastname@example.org School of Geosciences, Yangtze University, Wuhan 430100, China Research Institute of Petroleum Exploration & Development, Beijing 100083, China Vol.:(0123456789) 1 3 Journal of Petroleum Exploration and Production Technology Geological setting Internal structure anatomy of single sand body modelling The Xingshugang Oilfield is located in the middle of the Daqing Oilfield in northeast China, which is part of the Underground oil–water movement is affected by the struc- central depression area of the Songliao basin. The research tural characteristics of sand bodies (Yin et al. 2013). How- area is located in the North Development Zone of the ever, the digging of residual oil controlled by the sand body Xingshugang oilfield (Fig. 1). The development layer of configuration in the underground reservoir has become the the oilfield includes the Saertu, Putaohua and Gaotaizi major goal of oilfield development and adjustment after the oil-bearing groups in the Songliao Basin. The main oil sandstone reservoirs entered a later stage of development reservoirs are distributed in the Putaohua oil group and (Lin et al.2013). The representation of the sand body con- formed in the environment of the delta plain. The small figuration features are composed of three parts: (1) making layers are mainly P111, P112, P1211, P1212, P122, P131, a fine stratigraphic comparison of the logging curves of vari- P132, P1331 and P1332; the average single well drilling ous sections in the work area; (2) explaining and analysing sandstone thickness is 11.49 m; and the average single the logging lithofacies of the single well and dividing the well drilling in the effective thickness is 7.93 m. Non- sandstone phase and the mudstone phase; and (3) estab- main reservoirs are mainly distributed in other reservoirs lishing the subsurface reservoir configuration model by the of the Putaohua and Saertu reservoirs, which are formed multi-well fitting of the configuration model. in a delta front. The average single well-drilling sandstone The classification of the configuration in the research thickness is 62.39 m, and the average single well drill- area is to divide the single channel in the composite chan- ing in the effective thickness is 20.05 m. After several nel based on the sedimentary microfacies research. There rounds of encryption, the well space reached 30 m, which are mainly four ways to identify different single channels: provides rich and accurate data for model establishment. (1) finding inter-river sediments along channels, including overflowing sediments; (2) identifying abandoned chan- nels by logging curve characteristics (representing the end of point dam development and river diversion signs) and then determining the point dam boundaries; (3) identifying different river thicknesses; (4) different channels have dif- ferent sedimentary paleotopographies, which have different sediment-carrying capacities, where the logging response characteristics will be different. The abandoned channel can be summarized as a sudden abandonment type or a gradual abandonment type (Fig. 2). It is seen in the single well that the bottom of the abandoned channel and the bottom of the channel sand body are filled with sand, and there are two different filling methods in the upper part. The logging response characteristics of the upper part of the abandoned channel in the sudden abandonment type is where the SP curve is close to the baseline and the abandoned channel in the gradual abandonment type shows that the SP curve has toothed features. Therefore, after analysing the internal structure of the S21-1 sub-layer in the five types of facies (channel has perfect reservoir quality, tabulated reservoir has favorable Fig. 1 The map of regional geographic location of study area Fig. 2 Curve characteristics of abandoned river channel 1 3 Journal of Petroleum Exploration and Production Technology reservoir quality and untabulated reservoir has poor reser- and ebb and flow of single sand bodies in the three-dimen- voir properties) in the Xinger Middle Area, the composite sional space. Combined with the geological knowledge, channels are divided into single channels and the abandoned a single sand body provides a more reliable basis for the channels; point bars are identified; and the internal structure development of oil and gas. Therefore, single sand body of the point bars are depicted. The lateral mezzanine is iden- modelling technology is the key to establish an accurate tified, and the fine dissection of the reservoirs of the high geological model. However, the fine description of the sin- bending by-channel is completed (Fig. 3). gle sand body requires higher well density and high-reso- lution reservoir studies and is not suitable for highly heter- Internal structure modelling of single sand body ogeneous carbonate reservoirs. Based on the high-density well pattern and single sand body configuration research in The model established by the conventional stochastic mod- the Xingbei Research Area, this research applies the single elling technique often differs greatly from the reality, so sand body modelling technology to model the single sand it is difficult to accurately predict the distribution of an body structure and the physical property distribution of oil-bearing single sand body. In the middle and late stages the space in the research area (Fig. 4 shows the technical of oil and gas field development, a single sand body can route), which lays the foundation for a correct numerical clearly characterize the superimposition of multi-stage reservoir simulation. sand bodies in the reservoir and reveal the distribution Fig. 3 Profile 1 of reservoir architecture set in study area Fig. 4 The workflow of single sand body modeling 1 3 Journal of Petroleum Exploration and Production Technology across the space of the plane display phase. The sedimentary Single sand body structure modeling facies modelling can digitize the configuration model and then assign the parameters to the construction framework According to the identification requirements of Petrel soft- ware on the data identification, the data in the work area model, resulting in a reliable configuration model (Fig. 5). Through Petrel software, the single sand body structure are organized as follows: (1) collect well position data, well track data, stratified data and logging curve data; (2) check is subdivided by a human–computer interaction in the struc- tural model: (1) using the top–bottom data of sand body, and input the well position data, well track data and strati- fied data; (3) check and input all types of logging curve divide the structure into two lithofacies of mudstone facies and sandstone facies; (2) according to the sedimentary facies data; (4) select the appropriate grid size to guide the estab- lishment of the model according to the geological condi- distribution law, select the appropriate variation function, and the software automatically obtains a random model with tions in the research area and the later numerical simulation requirements. rough lithofacies distribution in the sequential indicator sto- chastic simulation method; (3) based on a random model The tectonic frame model is the foundation of single sand body modelling. This modelling is in the S21-1 work area and according to the plane sedimentary microfacies figure, confirm the distribution range of the channel sand body of a high bending meandering stream, covering an area of 3.1 km and has four layers with an average thickness of with the brushing tool of petrel software and then depict the sedimentary facies model as done in the explained results approximately 2 m. To better represent the interlayer mor- phology and reservoir heterogeneity, the grid density in the according to the fine single sand body configuration inter - pretation section (Fig. 6). Xinger Middle Area is designed to be 5 m × 5 m according to the actual geological condition and the well density, and Facies‑control property modeling of single sand the average thickness of a single grid in the vertical direc- tion is 0.2 m. Based on the operation load of the numerical body modelling and taking the geological contour line map in the research area as a template, the fine single sand body The three-dimensional heterogeneity model reflects the spatial distribution of the intragranular pore of reservoir, tectonic framework model is established. permeability and other physical property parameter fields in the form of a parameter entity. The porosity and per- Sedimentary facies modelling of a single sand body meability characterize the reservoir capacity and seepage capacity of the reservoir. The main purpose of facies- As most oilfields follow a sedimentary microfacies plan, conventional modelling does not describe the conforma- control modelling is to more accurately ref lect heteroge- neity. However, it is difficult for the fitting of the vari- tion sufficiently. In particular, the prediction of the single sand body reservoir and the anisotropy of the interlayer and ation function to reflect the spatial variation law of the geological conditions (the variation law of sedimentary point bar will enrich the remaining oil. Therefore, the con- figurational heterogeneity is particularly important in the facies and the spatial distribution of channel sand bodies, etc.). Therefore, based on the modelling of the sedimen- model. According to the research of the single sand body configuration, the major seven sections in this work area tary facies, this modelling is constrained by geological experience in removing the singular values. By finely can accurately show the vertical single sand body structure Fig. 5 Profile 1 of reservoir architecture model in study area 1 3 Journal of Petroleum Exploration and Production Technology Fig. 6 Facies models in study area. a Facies model in study area; b facies fence model in study area deploying the distribution of the sedimentary facies belt Numerical reservoir simulation and channel sand body, the model can strictly analyse the physical parameter distribution characteristics of the res- After several decades of development and improvement, ervoir, conduct a variation function analysis, and establish the numerical reservoir simulation technology has gradu- a fine porosity distribution model, permeability distribu- ally become irreplaceable in studying the remaining oil tion model and f luid saturation distribution model aiming (Guo and Liu 2014). Its purpose is to fit the dynamic pro- at different sedimentary facies in the stochastic model- cess of production and to study the law of oil–water move- ling method of the Gaussian simulation and assignment ment in a reservoir. Geological modelling is the precondi- method (Figs. 7, 8, 9). tion of numerical simulation. Numerical simulation is the key to geological modelling. The fine numerical simulation of reservoir is done to simulate the parameter field based on the parameter field of the fine reservoir description. The Fig. 7 Porosity model in study area. a Porosity model in study area; b porosity fence model in study area 1 3 Journal of Petroleum Exploration and Production Technology Fig. 8 Permeability model in study area. a Permeability model in study area; b permeability fence model in study area Fig. 9 Oil saturation model in study area. a Oil saturation model in study area; b oil saturation fence model in study area simulation results can accurately reflect the development pattern, proving that the conclusion can provide a potential process of oil and gas. The numerical simulation is mainly direction for tapping the remaining oil in the research area. based on the single sand body configuration model. The reasonable grid density enables the numerical simulation Parameter setting of numerical reservoir simulation to be carried out without roughening, completely preserv- ing the fine sand body configuration interpretation and The parameter field of numerical reservoir simulation plays spatial distribution model of the interlayer and other seep- a decisive role in the simulation results. Any irrational age barriers, and it can represent the oil and water move- parameter setting can cause non-operation of numerical ment law of a single sand body under interlayer control; simulation and mistakes in the simulation result. The physi- thus, the remaining oil distribution pattern in the study cal parameters of the reservoir and fluid are shown in the area can be quantitatively predicted. The simulation results following table (Table 1). are compared to the data of production wells and ana- The studies on reservoir engineering in the research area lysed according to the existing remaining oil distribution are deep, and the characteristics of the seepage of different 1 3 Journal of Petroleum Exploration and Production Technology Table 1 The physical properties of reservoir and fluid in the model Parameter items Water density (g/ Formation water Formation water Formation water Rock compressibil- Crude oil density (g/ 3 3 cm ) volume factor viscosity (mPa·s) compressibility ity (KPa-1) cm ) − 1 factor (KPa ) − 6 − 7 Parameter value 1.00 1.01 0.6 1.0 × 10 1.0 × 10 0.852 rocks have been summarized well. The phase-permeability typical work areas at the later stage of simulation (Fig. 10) characteristics and characteristic curves of various reservoirs are shown as follows: according to reservoir lithology, sedimentary facies and The S21-1 model sedimentary facies model in the study physical properties are obtained according to the character- area and the corresponding numerical simulation results of istics of the work area where the model is located; the appro- the plane show that the remaining oil is mainly distributed priate phase-infiltration curves, PVT and PVDO curves are at the mouth of the channel; the ends of the three types of selected. The simulation uses the concept model simulation reservoirs and the parts blocked by the interlayer. method. According to the actual well types and the perfora- It can be seen from the S21-1 model profile facies model tion conditions, the range of the injection and the produced in the research area and the corresponding numerical model- quantity of the oil wells and the water wells in the statistical ling results of this section (Figs. 11, 12) that the remaining model are statistically calculated. The reasonable production oil is mainly distributed in the obscured parts of the aban- and injection proration (actual injection-production ratio of doned channel and the obscured parts of the top interlayers the block is 1.11) and the water drive simulation to the ulti- of the point bar, shielded offshore sand bodies and three mate moisture content (fw = 98%) are conducted. types of facies, the edge of channel and the end of the sedi- mentary bodies. Numerical simulation analysis of reservoir Conclusion In the research area, high-bend distributary channel reser- voirs are developed. Their sedimentary types are similar to 1. In this project, a single sand body model is established those of high-bend rivers. There are argillaceous sides and by using the data of small well spacing. The space shape interlayers for blocking between the bulks of point bar sides of the sand body is accurately characterized by a human– of different stages as well as abandoned channel, overbank computer interaction method, which perfectly reflects sand and three types of reservoirs, etc. The sand body distri- the spatial distribution characteristics of the single sand bution model and plane simulation results of oil saturation of body skeleton and physical properties. However, due to Fig. 10 The map of facies model and oil saturation simulation result in study area. a Facies mode set in study area; b oil saturation simulation result set in study area 1 3 Journal of Petroleum Exploration and Production Technology Fig. 11 The profile 2 of facies model and oil saturation simulation result in study area. a Profile 2 of facies model; b profile 2 of oil saturation simulation result set in study area Fig. 12 The profile 3 of facies model and oil saturation simulation result in study area. a Profile 3 of facies model; b profile 3 of oil saturation simulation result set in study area the lack of internal structure scale, the cross-sectional of the well pattern is particularly important in secondary connections make the phase modes in the plane and the development. vertical direction contradictory. Therefore, the precision 3. The residual oil flow obtained by the numerical simula- improvement of the stratum contrast and configuration tion shows the effects of the single sand body configu- classification is an important method for improving the ration and interlayer on the remaining oil distribution. quality of the model. The residual oil pattern during the high water-containing 2. The distribution of the remaining oil is controlled by period is obtained; that is, the remaining oil controls various geological factors and requires a fine model to the oil and gas migration direction due to the interlayer, characterize the single sand body structure and interlayer abandoned channel and other impervious layers so that distribution. The small well distance data in this area oil and gas can be enriched around the channel and not only describes the model accurately but also greatly impervious layer. This model can provide an important reduces the model grid quantity, which facilitates the theoretical basis for the adjustment of the well pattern calculation of the numerical simulation and makes the in the oilfield and tapping the remaining oil in the next simulation results more accurate. Therefore, the density step. 1 3 Journal of Petroleum Exploration and Production Technology Acknowledgements We are also thankful for the generous finan- Qiu YN (1990) A proposed flow-diagram for reservoir sedimentologi- cial support from the National Science Foundation of China cal study. Petrol Explor Dev 15(1):85–90 (No. 41572081), the National Scientific Important Project (No. Wu SH, Li YP (2007) Reservoir modeling: current Situation and devel- 2016ZX05015-001-001). opment prospect. Mar Origin Petrol Geol 12(03):53–60 Yan BQ, Zhang XL, Yu LM, Zhang D, Jia GP, Yang YJ (2014) Point bar configuration and residual oil analysis based on core and dense Open Access This article is distributed under the terms of the Crea- well pattern. Petrol Explor Dev 41(5):597–603 tive Commons Attribution 4.0 International License (http://creat iveco Yin YS, Zhang CM, Yin TJ, Yu C (2013) Three dimensional archi- mmons.or g/licenses/b y/4.0/), which permits unrestricted use, distribu- tectural model of the high sinuous distributary channels on delta tion, and reproduction in any medium, provided you give appropriate plain. Geol Rev 59(03):544–550 credit to the original author(s) and the source, provide a link to the Yue DL, Wu SH, Cheng HM, Yang Y (2008) Numerical reservoir Creative Commons license, and indicate if changes were made. simulation and remaining oil distribution patterns based on 3D reservoir architecture model. J China Univ Petrol 32(02):21–27 Zhang CM, YIN TJ, Yu C (2013) Reservoir architectural analysis of References meandering channel sandstone in the delta plain based on the depositional process. Acta Sedimentologica Sinica 31(4):653–662 Zhao L, Liang HW, Zhang XZ, Chen L, Wang JC, Cao HL, Song XW Guo JC, Liu YX (2014) Numerical simulation of hydraulic fracture (2016) Relationship between sandstone architecture and remain- crossing natural fracture at orthogonal angles. Electron J Geotech ing oil distribution pattern: a case of the Kumkol South oilfield in Eng 19(N):3159–3172 South Turgay Basin, Kazakstan. Petrol Explor Dev 41(5):597–603 Hjellbakk A (1997) Facies and fluvial architecture of a high-energy Zhou YB, Wu SH, Yue DL, Liu ZP, Liu JL, Zhong XX (2010) Identifi- braided river: the Upper Proterozoic Seglodden Member, Varanger cation of single channel in compound distributary sandbody-case Peninsula, northern Norway. Sed Geol 114(1):131–161 of SII1-2b layer of west II region. 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Journal of Petroleum Exploration and Production Technology – Springer Journals
Published: May 31, 2018
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