红星地区建南区块吴家坪组优质页岩特征及水平井靶窗优选

Characteristics of High Quality Shales and Optimization of Horizontal Well's Target Window in Wujiaping Formation,Jiannan Block,Hongxing Area

红星地区建南区块位于四川盆地川东高陡褶皱带石柱复向斜带,是二叠系页岩气勘探有利区。以HY1、HY2两口钻井资料为基础,结合区内邻井的测录井资料,对吴家坪组二段(以下简称吴二段)页岩的小层划分、页岩平面展布、页岩品质及含气性、可压性及靶窗优选开展分析评价。结果表明,建南区块吴二段发育深水陆棚相暗色富有机质页岩,纵向上可划分为5个小层,平面上具有南薄北厚的展布特征。吴二段页岩具有高有机碳含量、高孔隙度、高含气量、高脆性矿物的地质特征,其中③小层具有厚度大、页岩品质优、含气性好、非均质性弱及破裂压力小等“地质+工程”甜点特征,确定其为水平井靶窗层段。HY1HF井实钻及试气结果表明,水平段穿行③小层的井段全烃平均超18%,测井解释Ι类页岩气层占比达98%,具有较高产气贡献率。研究成果为红星地区二叠系页岩气实现效益开发奠定了基础。

The Jiannan block in Hongxing area,located in the Shizhu complex syncline in the high and steep fold belt of eastern Sichuan,is a favorable area for Permian shale gas exploration.Based on the drilling data of two exploratory wells(HY-1 and HY-2)and adjacent wells in the area,this study evaluated the sub-layer division,plane distribution,quality,gas-bearing capability and compressibility of shale layers of the second section of Wujiaping formation(WJP-Ⅱ),and optimized the target window of horizontal wells.The results are as follows:the WJP-Ⅱdevelops dark organic-rich shale of deep-water shelf phases,which can be further divided into 5 layers in vertical,and is thin in the south and thick in the north.Shales of WJP-Ⅱis characterized by high organic carbon content,high porosity,high gas content,and high brittle minerals.The third sub-layer of WJP-Ⅱexhibits high thickness,excellent shale quality,fine gas content,high homogeneity and low fracturing pressure that matched the feature of“geology+engineering”sweet spot,therefore,it is the optimum target window for horizontal well.The drilling and gas testing of HY1HF show that the average proportion of total hydrocarbon from the third sublayer of the horizental penetrating exceed 18%.Log interpretation indicates that the proportion of class 1 shale gas layer reaches 98%,demonstrating its high contribution of gas production.The results from the present study lay solid foundation for profitable development of the Permian shale gas in the Hongxing area.