东胜气田盒1段地质特征及水平井储层改造对策

Geological characteristics of Shihezi 1 Member in Dongsheng gasfield and countermeasures against horizontal-well stimulation

为了明确鄂尔多斯盆地东胜气田下二叠统下石盒子组气藏水平井储层改造对策,以下石盒子组盒1段气藏地质特征为研究对象,系统分析了物探、测井、录井及化验分析等资料,总结了盒1段气藏构造、沉积、岩石学、物性、孔吼、隔夹层及气层叠置等特征,并提出了该气田盒1段气藏水平井相应的储层改造对策。研究结果表明:(1)盒1段气藏整体构造相对简单,呈北东高、南西低的单斜构造,发育近物源的冲积扇-辫状河沉积;(2)砂岩以浅灰色粗-中粒岩屑砂岩、岩屑石英砂岩为主,物性较差,砂岩孔隙类型以次生粒间溶孔和原生粒间孔为主,喉道以中小喉为主,盒1段储层属于特低孔-超低渗型储层;(3)盒1段地层厚度大,砂体发育,纵向多套气层叠置,其中发育两套和三套气层的占比为65%,气层间隔夹层主要为泥质隔夹层和物性隔夹层;(4)结合水平井目的层与相邻气层间隔夹层厚度提出有针对性的储层改造对策,隔夹层厚度大于等于7 m的设计思路为长缝压裂,其造缝长、应控制压裂规模,隔夹层厚度小于7 m的设计思路为穿层压裂,其造缝高、应加大压裂规模。结论认为,通过实施差异化的水平井储层改造对策提高了气井产能,为东胜气田盒1段的高效开发提供了依据。

In order to make countermeasures against horizontal-well stimulation for Lower Permian Lower Shihezi Formation, Dongsheng gasfield, large amount of geophysical, well-logging, mud-logging, and assay data on Shihezi 1 Member were analyzed systematically. And accordingly, several characteristics of these Shihezi 1 reservoirs were pointed out, including structure, sedimentation, petrology, physical property, pore and throat, interbed, and gas layer superimposition. In addition, some countermeasures against horizontal-well stimulation for these reservoirs were made.Results show that,(1) developed with proximal alluvial fan-braided river deposits, these reservoirs are structurally simple,presenting a monoclinal structure high in the northeast and low in the southwest;(2) for these sandstone reservoirs with light gray coarse-moderate lithic and lithic quartz sandstone as soul, their physical property is poorer, secondary intergranular dissolution pore and primary intergranular pore are the main pore types, and moderate and small throats are dominant, so that Shihezi 1 reservoirs are featured by extra low porosity and super low permeability;(3) in this thick Shihezi 1 Member with developed sandbody, various sets of gas layers are vertical superimposed, two or three sets accounting to 65%, and some interbeds between gas layers are mainly argillaceous and physical property ones;and(4) based on one thickness of the interbed between the target layer of horizontal well and its neighboring gas layer,certain stimulation countermeasures are made. According to their design idea, long fracturing is applied to the interbeds with the thickness≥5-7 m to ensure fracture length and control fracturing scale, and layer-penetrating fracturing is adopted for the interbeds with the thickness<5-7 m to guarantee fracture height and to increase fracturing scale.In conclusion, these countermeasures of horizontal-well stimulation may increase the productivity and provide the basis for the efficient development of Shihezhi 1 Member, Lower Shihezi Formation, Dongsheng gasfield.