川西南部地区沙溪庙组勘探目标研究

RESEARCH ON THE EXPLORATION TARGET OF SHAXIMIAO FORMATION IN THE SOUTH OF WEST SICHUAN

文章指出了川西南部地区侏罗系沙溪庙组储层的“裂缝性”和含气砂体的“隐蔽性”是气藏勘探两大难点;揭示了储层孔隙与砂岩组构的密切关系,孔隙更容易产生于长石含量高(大于37%)、碳酸盐胶结物含量低(小于5%)的中粒砂岩中,绿泥石—硅质—早期方解石—晚期方解石成岩相是砂岩形成较好储层的根本原因;其储层孔隙发育是产气的物质基础,若裂缝愈发育、产层段暴露越充分、单砂层愈厚,则气产量越高,射孔—加砂联作是提高气井产能的首推措施;气藏形成和高产的主要条件是足够厚的烃源岩(T3x5)、厚度适中物性良好的砂体(厚度不小于5m,Ф>5%)、裂缝是高产的必备条件。根据气藏形成和高产的主要条件,提出“泥包砂”裂缝—孔隙型气藏的勘探没必要完全按似层状整装裂缝—孔隙型气藏的勘探理论和模式,可适当迈开步伐。建议在非背斜构造(如大兴西—名山单斜等)加强对沙溪庙组的预探,对区内已钻含气构造沙溪庙组下一阶段的勘探提出了建议,还认为在以须家河组(T3x2)为钻探目的层的新区,兼探是了解沙溪庙组含油气性的重要途径。

In the paper,it is pointed out .that the two difficulties in gas reservoir exploration are the reservoir's being fractured and sandbody' s being concealed in Shaximiao . Formation of Jurassic in the south part of West Sichuan; the reservoir porosity is closely related to the sandstone fabric, the pores being easy to be formed in the medium-granular sandstones with high feldspar content (>37%) and low carbonate cement content(3 x5) and the sandbodies with a moderate thick (≥5 m) and good petrophysical property (φ 5%) ;and the development of fractures is the necessary condition of obtaining high gas well productivity. For this reason, it is. proposed that the exploration theory and model .of the analogously layered and integral fracture-pore, gas reservoir have no need to be wholly used for the 'sandstone-inmudstone' fracture-pore .gas reservoir exploration, so that it is suggested that the Shaximiao Formation exploration should be. strengthened in some non-anticlinal structures as Daxingxi-Mingshan monocline, etc, and in the gas-bearing structures drilled ; and it is considered that, in new exploration areas taking the Xujiahe Formation (T3x2) as a drilling target zone, a concurrent exploration is an important way of surveying the hydrocarbon potential of Shaximiao Formation in the areas.