摘要：

珠江口盆地L油田ZJ10A、ZJ10B层系为低渗礁灰岩主力储层，ZJ10层A、B两个灰岩油藏的岩心实测渗透率平均值为45.9 mD，中值为21.5 mD。储层非均质性强、裂缝发育。油田开发初期面临见水快、产量递减显著、能量亏空等问题。作为南海东部首个注水开发的裂缝性低渗礁灰岩油田，其井网密度低、取心段少、成像测井资料匮乏，传统方法难以精准刻画井间小尺度裂缝，裂缝主控因素与发育规律不明，制约油藏高效开发。针对上述难点，本文以储层地质力学理论为指导，整合多源数据，构建“古岩石物理参数校正－地应力模拟－裂缝预测－开发对策”一体化技术体系。基于东沙运动背景恢复古埋藏深度(较现今浅600~700 m)，校正现今测井数据获取古岩石力学参数；采用有限元数值模拟，施加33 MPa北西向古应力，量化应力对裂缝的控制作用，结合成像测井及实钻数据验证预测可靠性。研究表明，目标储层主要发育北西向、近南北向两组高角度共轭剪切构造裂缝(占比91%)，形成受控于东沙运动北西向挤压应力。横向上裂缝高发于1d井东部及2d井南部构造高点，南部断层仅转折处裂缝发育增强；纵向上ZJ10A层裂缝密度(0.13~0.31条/m)高于ZJ10B层(0.04~0.28条/m)，且自上而下递减。裂缝预测结果经实钻验证，82%的样本绝对误差小于等于0.7条/m，预测可靠。同时，裂缝密度与生产初期含水上升率呈正相关，据此将生产井划分为4类，并针对不同类型的生产井提出了所对应的稳油控水对策。本次研究构建的一体化技术流程有效解决了海上少井条件下低渗礁灰岩小尺度裂缝定量预测难题，完善了相关技术体系。明确的裂缝分布规律及4类井差异化稳油控水对策，可为L油田开发调整提供科学依据，也为海上同类油藏精细勘探开发提供技术借鉴。

关键词: 低渗, 礁灰岩, 裂缝精细表征, 开发效果, 稳油控水

Abstract:

The ZJ10A and ZJ10B formations of the L Oilfield in the Pearl River Mouth Basin are the main low-permeability reef limestone reservoirs. The average measured core permeability of the two limestone reservoirs, A and B, in the ZJ10 layer is 45.9 mD, with a median value of 21.5 mD. The reservoirs are characterized by strong heterogeneity and well-developed fractures. In the early stage of oilfield development, problems such as rapid water breakthrough, significant production decline, and energy depletion were encountered. As the first water-flooded fractured low-permeability reef limestone oilfield in the eastern South China Sea, it has low well-pattern density, few coring intervals, and insufficient imaging logging data. With traditional methods, it is difficult to accurately characterize small-scale inter-well fractures. The main controlling factors and development patterns of fractures are unclear, which restricts the efficient development of the reservoir. To address the above difficulties, guided by reservoir geomechanics theory, this paper integrates multi-source data and constructs an integrated technical system of “paleo-petrophysical parameter correction - in-situ stress simulation-fracture prediction-development countermeasures”. Based on the background of the Dongsha movement, the paleo-burial depth (600~700 m shallower than the present) was restored, and the paleo-petrophysical parameters were obtained by correcting the present logging data. Finite element numerical simulation was adopted, with a 33 MPa northwestward paleo-stress applied to quantify the controlling effect of stress on fractures. The reliability of the prediction results was verified using the fracture development is only enhanced at image logging and actual drilling data. The results show that the target reservoirs are mainly developed with two sets of high-angle conjugate shear structural fractures (accounting for 91%) trending northwest and nearly north-south, whose formation is controlled by the northwestward compressive stress during the Dongsha Movement. Laterally, the high fracture development areas are concentrated in the structural highs in the east of Well 1d and the south of Well 2d, and the fracture development is only enhanced at the turning points of the southern fault. Vertically, the fracture density of the ZJ10A formation (0.13~0.31 fractures/m) is higher than that of the ZJ10B formation (0.04~0.28 fractures/m), and it decreases from top to bottom. The fracture prediction results were verified by actual drilling data, with the absolute error of 82% of the samples being ≤ 0.7 fractures/m, indicating reliable prediction. Meanwhile, there was a positive correlation between the fracture density and the water cut rise rate in the early production stage. Based on this, the production wells were divided into 4 types, and corresponding oil stabilization and water control measures were proposed for each type. The integrated technical process constructed in this study effectively solved the problem of quantitative prediction of small-scale fractures in low-permeability reef reservoirs under the condition of few actual measurement data. The study indicates that the constructed integrated technical system effectively solves the problem of quantitative prediction of small-scale fractures in low-permeability reef limestone under the condition of few offshore wells and improves the relevant technical system. The clarified fracture distribution patterns and differentiated oil stabilization and water control countermeasures for the 4 types of wells can provide a scientific basis for the development adjustment of the L Oilfield and also provide technical reference for the fine exploration and efficient development of similar reservoirs at the Sea.

Key words: low permeability, reef limestone, fine fracture characterization, development effect, oil stabilization and water control

中图分类号: 

• P618.13

• TE349