龙门山金马—鸭子河推覆构造带雷四段储层脆性与裂缝预测

Reservoir brittleness and fracture prediction of Member 4,Leikoupo Formation in Jinma-Yazihe nappe tectonic belt,Longmen Mountain

龙门山金马—鸭子河推覆构造带展现出盆—山结合区域地表、地下地质条件复杂的"双复杂"特点,致使储层和裂缝预测难度较大。为此,结合区内地质、地球物理特征,在分析白云岩、灰岩、膏(盐)岩的测井响应差异的基础上,基于地震数据计算岩石脆性与裂缝参数,并以此研究优质脆性储层空间展布和裂缝发育特征,且得出以下认识:(1)根据测井和地震数据分别计算的脆性系数清晰地刻画了白云岩、灰岩储层与上覆泥岩、下伏膏(盐)岩的脆性差异,并据此研究了优质脆性储层空间展布和裂缝发育特征;(2)雷四上亚段储层中存在构造和非构造两类裂缝,其展布规律与构造、沉积等多种内外因素密切相关,且在气藏圈闭内的不同构造部位的裂缝发育程度存在差异;(3)充分利用不同岩性的脆性差异及脆性与裂缝之间的密切关系,能更深刻地认识优质储层的地质特征,但受脆性系数计算精度、地震分辨率等客观因素制约,尚难以精确定量预测脆性储层中的裂缝;(4)雷四上亚段的孔隙度较高、微裂缝较发育、脆性较强的白云岩和灰岩储层,应是气藏开发中选点、选层的关键目标。上述认识在金马—鸭子河推覆构造带PZ1、YaS1等井的实钻资料中获得了验证。

Jinma-Yazihe nappe tectonic belt in Longmen Mountain is characterized by complicated surface and subsurface,and it is very difficult to predict reservoirs and fractures in this belt.According to geological background and geophysical features in the area,and logging responses of dolomite,limestone,and gypsolith,we calculate rock brittleness and fracture parameters based on seismic data,and obtain the following observations:(1)The spatial distribution of high-quality brittle reservoirs and fracture development characteristics are predicted based on brittleness differences between dolomite and limestone reservoirs and overlying mudstones,and between dolomite and limestone reservoirs and underlying gypsum rocks calculated on logging and seismic data.(2)In the upper sub-Member of Leikoupo Formation,there are structural and nonstructural fractures;their distribution has a close relationship with tectonic,sedimentation,and other factors;and fractures developed differently in gas traps.(3)High-quality reservoir characteristics can be clearly identified based on rock brittleness differences and relationships between the brittleness and fractures;however the fractures in brittle reservoirs cannot quantitatively be predicted due to brittleness coefficient accuracy and seismic data resolution.(4)In the upper submember of Member 4,Leikoupo Formation,dolomite and limestone reservoirs have high porosity,strong brittleness,and developed fractures,they should be key targets for the gas development.The above observations have been approved by the drilling results of Well PZ1 and Well YaS1.