泸州区块深层页岩气富集高产主控因素

Main controlling factors of enrichment and high-yield of deep shale gas in the Luzhou Block, southern Sichuan Basin

要实现深层页岩气的规模效益开发,明确其富集高产主控因素至关重要。为此,以四川盆地川南地区泸州区块上奥陶统五峰组—下志留统龙马溪组页岩为研究对象,基于地震、钻井、测井及岩心分析化验资料,深入研究该页岩气区块的构造特征、沉积特征、储层特征及可压性,并结合气井生产动态分析页岩气井高产的主控因素。研究结果表明:①泸州区块龙一1亚段在纵向上存在着两套Ⅰ类储层,一套为储层厚度介于10~20 m的龙一11-3小层,另一套为储层厚度介于3~10 m的龙一14小层,且两套储层的含气饱和度、总含气量和脆性矿物含量都高;②Ⅰ类储层厚度越大、其水平井段钻遇的长度越长,气井初期产量就越高,在Ⅰ类储层钻遇长度相同的情况下,泸州区块气井的测试产量较长宁、威远区块高出10%~25%;③深水陆棚沉积中心控制了泸州区块优质页岩的展布,在低陡构造及异常高压背景下,高角度天然裂缝发育有利于游离气的聚集,且该区块脆性矿物含量高,人工压裂后易形成复杂缝网,从而使该区块页岩气井易获得高产。结论认为,位于深水陆棚沉积中心、在异常高压背景下发育高角度天然裂缝的低陡构造有利于页岩气的富集高产。

The key to the scale development of deep shale gas lies in a better understanding of the main controlling factors for its enrichment and high-yield.In this regard,the high-quality shale of the Upper Ordovician Wufeng-Longmaxi Formations in the Luzhou Block,southern Sichuan Basin,was taken as the research object.Based on drilling,logging,seismic and analytical test data of a typical core well there,an in-depth study was conducted on the tectonic,sedimentary,and reservoir characteristics and compressibility of shale in this study area.On this basis,combined with production performance,the main controlling factors of a high-yield shale gas well were discussed.The following findings were achieved.(1)There are two sets of type-I reservoirs with high gas saturation,high total gas content and high brittle mineral content vertically.One is S1l111-3 sub-layers with a thickness of 10-20 m,the other is S1l114 sub-layer with a thickness of 3-10 m.(2)The thicker the type-I reservoir,the longer the targeted horizontal sections,and the higher initial production rate of a horizontal shale gas well.Under the same scenario,the trial test production rate of a shale gas well in the Luzhou Block is 10-25%higher than that in the Changning and Weiyuan blocks.(3)The deep shelf sedimentary center controls the distribution of high-quality shale in the Luzhou Block,and under the setting of low deep structure and abnormally high pressure,those well-developed high-angle natural fractures are good for the accumulation of free gas,and due to a high brittle material content there,the complex fracture networks are easily formed by fracturing,as a result,a high yield will be easily achieved for a shale gas well in this study area.In conclusion,high-yield and enrichment of shale gas reservoirs should be under such favorable conditions as being located in the deep-water shelf sedimentary center and with well-developed high-angle natural fractures under the setting of low steep structure and abnormally high pressure.