草古潜山裂缝性碳酸盐岩油藏油水界面确定及有利区预测

草古地区奥陶系潜山油藏岩性以碳酸盐岩为主,储集空间和渗流通道主要为裂缝,其次为溶蚀孔洞。草古潜山油藏具有较高的初始产能,但开发过程中水侵严重,导致储层流体性质判别和油水界面确定困难,极大地影响了草古潜山油藏的生产开发。为了更有效地对草古潜山油藏进行生产开发,首先,以成像测井标定常规测井建立了储层识别与分类标准,利用电法和非电法测井组合图版进行流体性质识别;其次,结合测井解释和试采结果确定油藏原始油水界面,并且在考虑断层和裂缝影响的条件下,提出了一种单井动态油水界面预测方法;最后,叠合储层分布、裂缝分布与剩余油分布确定了开发潜力有利区。研究结果表明:草古潜山油藏储层可分为Ⅰ、Ⅱ、Ⅲ类;声波～深电阻率/浅电阻率(AC～RD/RS)图版和自然电位*深电阻率/浅电阻率～深电阻率(SP*RD/RS～RD)图版结合可有效区分油层、水层和干层;油藏原始油水界面深度为920 m,考虑垂直裂缝影响的油水界面计算公式能较准确确定动态油水界面;过断层的井初期含水率高,远离断层的井含水率上升速度快;平均裂缝孔隙度越高、Ⅰ类储层占比越高,含水率上升速度越快;A113、A11-9、A1-4井区具有开发调整潜力。提出的油水界面及有利区的确定方法为后期油藏开发提供了依据,也为其他裂缝性油藏的开发提供了新思路。

Oil-water interface determining and favorable zone prediction of fractured carbonate reservoir in Chaogu buried hill

The lithology of Ordovician buried hill reservoirs in the Chaogu area is dominated by carbonate rocks, and the reservoir spaces and seepage channels are mainly fractures, followed by dissolved cavities. Chaogu buried hill reservoirs have high initial productivity, but severe water intrusion during the development process makes it difficult to identify reservoir fluid properties and oil-water interfaces, which greatly affects the production and development of Chaogu buried hill reservoirs. In this paper, comprehensive use of core analysis, logging, production and development data, has carried out research on reservoir identification and classification, reservoir fluid property discrimination, reservoir oil-water interface determination, reservoir water cut influencing factors analysis, and finally determined the development favorable zone. The research results show that: Chaogu buried hill reservoirs can be divided into types I, II, and III. The combination of AC~RD/RS plot and SP*RD/RS~RD plot can effectively distinguish reservoir, water layers and dry layers. Well logging interpretation and production results determine that the original oil-water interface of the reservoir is 920 meters. The oil-water interface calculation formula which considers the influence of the vertical fractures can more accurately determine the dynamic oil-water interface. The initial water content of wells that cross the fault is high, and the water content of the wells that far away from the fault rises quickly. The higher average fracture porosity, the higher proportion of type I reservoirs, the faster water content rises. Based on the reservoir distribution, fracture distribution and remaining oil distribution area of Chaogu buried hill, it is determined that the A113, A11-9 and A1-4 well areas have development and adjustment potential. The determination of oil-water interface and favorable zone in Chaogu buried hill provides a basis for reservoir development in the later stage, and also provides a new idea for the development of other fractured reservoirs.