安棚油田储层裂缝特征及其形成期次分析

安棚油田深层系储层属扇三角洲相沉积,储层岩石的成分成熟度和结构熟度均较低,岩性胶结致密,具有特低孔隙度和特低渗透率特征.储层中天然裂缝较发育,以高角度或垂直裂缝为主,裂缝中常有部分次生方解石充填,该类破裂成组出现.裂缝性质包括张性破裂和剪切破裂,裂缝成因类型是与区域拉张应力有关的区域性裂缝.与局部构造变形作用无关.通过对裂缝充填物——次生方解石进行稳定同位素测定,对储层岩石进行声发射实验,确定了储层岩石的破裂期次,研究得到安棚油田储层的天然破裂期次有4期,第二期是主要的破裂期.分析了影响裂缝发育程度的两个方面因素:一为区域构造应力场强度;二为储层岩石的力学性质及厚度.并建立了储层厚度与裂缝间距的相关方程,该关系式可应用于裂缝预测.

Reservoir fracture characteristics and generation analysis in Anpeng oilfield, Biyang depression

The paper described the features of extra-low-permeability reservoirs in deep-buried zones of Anpeng oilfield,Biyang depression, Henan province,central China.The buried depth of reservoir is 2 800~3 100 m,The reservoirs are composed of fan-delta facies deposits.The composition and texture maturity of reservoir rocks is lower.The reservoir porosity distribution ranges 5% to 6%,the permeabilitydistribution ranges 1×10-3 to 2×10-3 μm2.There are more natural fracture developed in Anpeng oilfield.Research on coring and FMI logging indicates that the main fracture occurrence in reservoirs is in a high degree or in vertical.The vertical fracture groups occurrence in reservoir.Adopt advanced technique-oriented coring to get the fracture azimuth.The rosette azimuth diagram shows that the open fracture azimuth range 90°to 110°.The fracture length distribution range 4 to 30 cm,the fracture apertures are smaller than 1 000 p.m, the density of fracture is 0.7 per meter,the formation fracture porosity range 0.2% to 0.3%.There are some secondary calcite fillings in the side of fractures.The space between fractures is 2 to 3 cm.It includ the extention fractures and shear fractures.The regional tensile stress is the causes of fracture.The secondary calcite stable isotope measurate of the fillings in fracture and the acoustic emission tests of the reservoir rocks indicate that there are four fracture generations.The second generation is the main fracture period.There are two main factors to affect the fracture developing:one is the structure stress field;another is the nature and the thickness of the reservoirs.Finally,the relationship between thicknes and fracture space is established.