新疆中拐地区石炭系火山岩构造裂缝发育特征、期次及渗流特征

Development Characteristics,Formation Stages and Seepage Characteristics of Tectonic Fractures of Carboniferous Volcanic Rocks in Zhongguai Area,Xinjiang

中拐地区石炭系火山岩储层性能受到不同期次构造裂缝控制,裂缝对油气的富集及产能具有重要影响,研究构造裂缝发育特征、形成期次及渗流特征将为有效评价与开发有利储层提供依据。该区主要发育高角度缝和斜交缝,裂缝发育方位包括近EW向(270°±10°)、NW向(300°±15°)、NE向(45°±15°)和SN(0°±10°)。利用裂缝充填物成分及切割关系、裂缝充填物包裹体测温和岩石声发射试验等研究结果,结合构造演化历史,认为该区构造裂缝至少可以划分为4期:第1期构造裂缝形成于海西构造运动中期,充填物为细粒方解石及绿泥石,包裹体均一温度为75~82℃;古构造应力值为49.6 MPa;第2期构造裂缝形成于海西构造运动晚期,充填物为石膏,包裹体均一温度为92~97℃,古构造应力值为39.9 MPa;第3期构造裂缝形成于印支构造运动期,充填物主要为较粗粒方解石,包裹体均一温度为106~112℃,古构造应力值为34.1 MPa;第4期构造裂缝形成于燕山构造运动期,该期裂缝几乎未充填,古构造应力值为26.5 MPa。受现今应力场的影响,近EW向裂缝的张开度大、渗透率高,是布置开发井网时优先考虑的方向,随着油田开发,不同组系裂缝渗透性的动态变化各不相同,要及时进行相应的井网调整。

The properties of Carboniferous volcanic reservoirs in Zhongguai area are controlled by different stages of structural fractures,which have an important influence on the enrichment and productivity of oil and gas.It is of great significance to study the developmental characteristics of structural fractures,the formation phases and the seepage characteristics in order to provide evidence for effectively evaluating and developing the favorable reservoirs.There are mainly high-angle and oblique cross-joints in this area.The fractures develop in the orientations of near EW（270°±10°）,NW（300°±15°）,NE（45°±15°）and SN（0°±10°）.The research results of the compositions and cutting relations of fracture fillings,the homogenization temperature of the fracture packing inclusions and the acoustic emission test,combining with the tectonic evolution history suggest that the structural fractures in this area should be divided into at least four stages.The first stage of structural fractures was formed in the middle Hercynian tectonic movement.The filling was fine-grained calcite and chlorite.The homogenization temperature of the inclusions was 75-82℃ and the paleo-tectonic stress was 49.6 MPa.The second stage of structural fractures started in the Hercynian structure in the later period of movement.The filling was gypsum.The homogenization temperature of the inclusions was 92-97℃ and the paleo-tectonic stress was 39.9 MPa.The third-stage of tectonic fractures were formed during the Indo-Chinese tectonic movement,and the filling mainly consisted of coarse.The calcite and granulite homogenization temperature is 106-112 ℃,and the palaeotectonic stress is 34.1 MPa.The fourth stage of tectonic fractures happened during the Yanshanian tectonic movement.The fractures were barely filled during this period,and the palaeotectonic stress was 26.5 MPa.Affected by the current stress field,the near-EW fractures have a large opening and high permeability,which are the prior directions for the layout of well layout.With the development of oilfields,the dynamic changes of fracture permeability in different group systems are different and should appear in time with the corresponding well adjustment.