洛带蓬莱镇组地应力特征及压裂应用研究

Stress Characteristics of Penglaizhen Formation in Luodai Gasfield and Its Application to Fracturing

洛带气田蓬莱镇组储层致密,需通过水力压裂改造才能获得工业产能,但压后评估发现效果差别较大。地应力特征影响着水力压裂施工所产生的裂缝产状等参数,在压裂液及支撑剂的选择上也需考虑地应力特征,因此,要科学、合理、高效开发该气藏,实施合理的水力压裂增产措施,开展地应力特征研究十分必要。利用水力压裂资料和测井选择弹簧组合模型确定出单井的地应力剖面及各层段地应力分布,分析了地应力剖面特征,确定了地应力剖面类型,分析了各种类型裂缝产状、压后效果。发现JP33及以上储层最小水平主应力值小于27MPa,为降低施工成本,可选用石英砂作支撑剂,JP33之下高于27MPa储层可选低密度陶粒;高低高型地应力剖面压裂缝高度小,改造后的效果好,应优选该类剖面气层进行压裂改造,低高低型压裂效果差,应避免对该类型气层进行压裂。

In Ludai gasfield,Peilaizhen Formation is tight. So, commercial gas can be obtained from this reservoir only by hydraulic fracturing. However,it is found that after fracturing,there is a big difference among fracturing effects. Stress characteristics may affect some parameters such as fracture occurrence which is produced from hydraulic fracturing. In addition,stress characteristics should be taken into consideration when both fracturing fluid and proppant are chosen. Therefore,it is very necessary to study stress characteristics in order to implement reasonable hydraulic fracturing and further effectively develop a gas reservoir. In this study, stress profile of single well and stress distribution of individual layer are at first determined by an assembled springs model; and then, some characteristics of stress profile are analyzed; thirdly,the type of stress profile is determined; at last,occurrence of various fractures and post-fracturing effect are researched. For J3p 3 3 or above which their minimum horizontal principal stress is less than 27 MPa,quartz sand can be selected as proppant to decrease an operation cost; for below J3p 3 3 with their minimum horizontal principal stress more than 27 MPa,ceramsite with low density can be chosen as proppant; a kind of stress profile in form of high- low- high should be optimized to carry out fracturing; and another kind of stress profile in form of low-high-low should be avoided.