川中安岳气田须二段致密砂岩气藏开发有利区优选

Preferential selection of favorable development areas of tight sandstone gas reservoir in the second Member of Xujiahe Formation in Anyue gas field of central Sichuan Basin

文中针对安岳气田须二段致密砂岩气藏开展了储层甜点精细刻画,结合气井生产动态分析,明确了气藏效益开发的主要影响因素。有效储层规模是气井高产稳产的关键因素。将须二段划分为5个小层,储层甜点主要发育于工区中西部X2-5,X2-4小层的水下分流河道叠置砂体中,为中—中粗粒长石石英砂岩、岩屑石英砂岩,发育粒间溶孔、粒内溶孔和微裂缝,属于孔隙型、裂缝-孔隙型储层。确定气藏效益开发的单井储层厚度下限为9 m,含气饱和度下限为55%。裂缝发育是气井初期高产的重要因素,但高导裂缝水侵导致气井快速递减,影响开发效益。Ⅰ类气井多在孔隙型储层,尽管初期产气量中等偏低,但稳产期较长,单井EUR(Estimated Ultimate Recovery,最终可采储量)高;裂缝-孔隙型储层初期高产,但稳产期短,EUR偏低。为主动防水、控水,井位部署应避开高导裂缝带,优选射孔层位,避开含水层,控制生产压差和压裂缝高。综合EUR、气层厚度、储量丰度等因素优选3个效益开发有利区。

In this paper,fine characterization of reservoir distribution has been studied for tight sandstone gas reservoir in the second member of Xujiahe formation in Anyue gas field of central Sichuan Basin.Combined with gas well production performance analysis,the main factors influencing efficient gas reservoir development are defined.Effective reservoir size is the key factor for high and stable production of gas wells.The reservoir sweet point is mainly developed in the superimposed sand bodies of the subaqueous distributary channel of the X2-5 and X2-4 subbed in the central and western part of the working area,which are medium grain-medium coarse grain feldspar quartz sandstones and lithic quartz sandstones.Intergranular dissolved pores,intragranular dissolved pores and micro-fractures in the reservoir are developed,belonging to pore type and fracture-pore type reservoir.The lower limit of single well reservoir thickness and gas saturation is 9 m and 55%respectively.The development of fractures is an important factor for high initial production of gas wells,on the other hand,water invasion along high conductivity fractures causes rapid decline of gas wells and thus leads to poor overall development benefit.TypeⅠgas wells are mostly pore type reservoirs with low-middle daily gas production in initial stage,but with long stable production period and high single well EUR(estimated ultimate recovery).Fracture-pore type reservoirs are characteristic of high initial production,short stable production period and low single well EUR.In order to realize the prevention and controlling of water invasion,it is necessary to take the initiative to avoid the high conductivity fracture zone in well placement,optimize perforation layer,keep away from aquifer and control production pressure difference and fracture height.Three favorable areas for economic and efficient development are preferentially selected based on EUR,thickness of gas reservoir,abundance of reserves,ect.