川南河包场构造须二段有效储层地震预测

SEISMIC PREDICTION OF EFFECTIVE RESERVOIRS IN THE SECOND MEMBER OF XUJIAHE FORMATION (T_3x_2) IN HEBAOCHANG STRUCTURE, THE SOUTHERN SICHUAN BASIN

河包场低平构造上三叠统须家河组二段砂岩生储盖组合良好,油气资源丰富。已有的勘探实践证实,储层品质分布很不均一,只有钻遇有效储层(孔隙度大于8%,单层厚度大于10m)才可获得工业气流,故有效储层预测是河包场构造须二段气藏描述的关键。为此,运用层序地层学原理及研究方法,将该区须家河组划分为四个地震层序,研究发现须二段有效储层主要发育在层序2的低水位体系域。通过分析层序2低水位体系域的地质、测井、地震等特征,采用地震属性和波形分类技术,确定该层序属于河口坝沉积微相区。同时,通过对层序1厚度的研究,认识了中三叠统侵蚀面岩溶古残丘的分布规律。河口坝沉积微相和侵蚀面岩溶古残丘的分布区域控制了须二段有效储层的分布,在对该有效储层有利区定性预测的基础上,采用高精度地震反演技术完成了对有效储层的定量预测。经钻井检验,预测与实钻吻合,所钻井均获得工业气流。

T3x2 Sandstones in Hebaochang low-amplitude structure are excellent in combinations of source-reservoir-cap rocks and are rich in petroleum resources. Exploration practices show that the distribution of reservoir quality is non-uniform and commercial gas flow can be tested only when effective reservoirs with porosity over 8% and single layer thickness over 10 m are penetrated, thus prediction of effective reservoirs is the key to the description of gas reservoir in T3x2 of Hebaochang structure. The Xujiahe Formation in the study area is divided into 4 seismic sequences by using the principles and methods of sequence stratigraphy. The effective reservoirs in T3x2 are mainly developed in the low system tract of sequence 2. The geological, logging and seismic features of T3x2 in the low system tract of sequence 2 are analyzed, and this sequence is determined to be mouth bar microfacies by using seismic attributes and waveform grouping techniques. Meanwhile, the distribution of karst fossil residual hills on the Middle Triassic erosion surface is determined through studying the thickness of sequence 1. The distribution area of the mouth bar microfacies and karst fossil residual hills on the erosion surface control the distribution of effective reservoirs in T3x2. Based on a qualitative prediction of the favorable distribution areas of the effective reservoirs, quantitative prediction of the effective reservoirs are performed by using high resolution seismic inversion technique. Drilling results are in good coincidence with the predictions and commercial gas flows are tested in all the wells drilled.