苏里格气田优质储层控制因素

FACTORS CONTROLLING RESERVOIRS WITH HIGH QUALITY IN GIANT SULIGE GAS FIELD

苏里格气田是我国发现的第一个世界级储量的大气田,该气田的气藏分布严格受储层的控制。储层具有埋藏深度大(超过4000m)、深埋时间长(距今150Ma以上)、成岩演化程度高(晚成岩B—C阶段)、物性较好(是鄂尔多斯盆地上古生界最好的储集层)的特点。为此,对该气田优质储层的控制因素进行了综合分析。结果认为,优质储层的分布主要受沉积环境(石英含量、碎屑粒度)、异常高压、古地形、成岩作用、裂缝发育程度等因素的控制:石英含量大于90%、特别是大于95%时,储层孔隙度、渗透率明显变好;成岩作用的差异性使得中粗粒砂岩的物性较好,而中细粒砂岩物性较差;异常高压对优质储层的发育具有一定的保护作用;裂缝对储层物性有着较大的改善作用;砂岩中绿泥石含量和孔隙度具有明显的正相关性,绿泥石含量可以作为指示优质储层发育的指标。

Sulige gas field is the largest gas field in China where the distribution of gas pools is strictly controlled by the reservoirs. The reservoirs in this gas field are characterized by large burial depth (>4000 m), long time of deep burial (>150 Ma), high degree of diagenetic evolution (Late Diagenetic Stage B-C) and good petrophysical properties (the best in the Upper Paleozoic in the Ordos Basin). The controlling factors of high-quality reservoirs are comprehensively analyzed in this paper. The results show that the distribution of high-quality reservoirs is mainly controlled by sedimentary environment (quartz content and grain size), anomalous pressure, ancient landform, diagenesis, and fracture development, etc. The porosity and permeability increase significantly when the quartz content is more than 90%, especially over 95%. The poroperm characteristics of medium-to-coarse grained sandstones are relatively good while that of medium-to-small grained sandstones are relatively poor due to the difference of diagenesis. Anomalous pressures are helpful to the development of high-quality reservoirs. Fractures can greatly improve the petrophysical properties of the reservoirs. Chlorite content of the sandstones is obviously seen in positive correlation with their porosity, thus it can be used as an indicator of high quality reservoirs.