南川常压页岩气地质特征及水平井参数优化研究——以东胜区块SY1井区为例

Study on geological characteristics of atmospheric shale gas and optimization of horizontal well parameters in Nanchuan——Take the well SY1 area of Dongsheng Block as an example

常压页岩气为低渗、特低渗储层,一般采用水平井多段压裂后形成复杂缝网才能有效动用。针对南川东胜区块位于盆缘过渡带复杂区,构造和地应力复杂,井位难部署等问题,以东胜区块SY1井区为例,开展构造特征、储层特征等地质特征研究,同时优化水平段方位及段长,并进行相关性正交试验。结果表明:1)SY1井区块构造呈单斜形态,地层相对平缓(0°~15°),内部次级断层不发育;2)通过岩心观察、薄片、氩离子抛光扫描电镜等多种研究方法确定SY1井区高阻缝发育,以中高角度高阻缝为主,为北东东—南西西向;3)东胜区块地应力呈现由南向北、由主体向两翼增大的趋势,最大水平主应力为50~80 MPa,其中SY1井区最大地应力为65~75 MPa;4)东胜区块SY1井区水平井部署方位与最小主应力夹角为20°,部署段长为1800 m时裂缝改造体积最大,单井评估最终可采储量EUR相对最高。以上成果认识,对东胜区块北部SY1井区井网优化部署提供了依据,为实现常压页岩气经济效益开发奠定了基础。

Atmospheric shale gas is a low permeability reservoir,complex fracture network is formed after multi-stage fracturing of horizontal wells generally.The Dongsheng Block in southern Sichuan basin is located in the transitional zone of the basin margin,which is complicated in structure and geostress,and difficult to deploy wells.In this paper,taking the well SY1 area of Dongsheng Block as an example,the geological characteristics such as structural characteristics,reservoir characteristics and other geological characteristics are studied.Meanwhile,the orientation and length of horizontal section are optimized,and correlation orthogonal test is carried out.The result of research shows that:1)The structure of block SY1 is monoclinic,the formation is relatively flat(0°~15°),and there is no secondary fault in it;2)High fracture development in the well SY1 area was determined by various research methods such as core observation and thin section argon ion polishing and scanning electron microscopy,and the high fracture development was dominated by medium-high angle high fracture,with a direction of NEE-SWW;3)The in-situ stress in Dongsheng Block increases from the south to the north,from the main body to the two wings,and the maximum horizontal principal stress is 50~80 MPa,among which the maximum in-situ stress in well SY1 block is 65~75 MPa;4)In the well SY1 area of Dongsheng Block,the angle between the horizontal well deployment orientation and the minimum principal stress is 20°.When the deployment section length is 1800 meters,the fracture volume is the largest,and the EUR of single well is relatively the highest.The understanding of the above results provides a basis for the optimal deployment of well pattern in the well SY1 area in the northern part of Dongsheng Block,and lays a foundation for the economic development of atmospheric shale gas.