The Application Of Low-cost Geosteering Technology In The Drilling Of Changning Shale Gas Horizontal Wells

Since 2008,the exploration of shale gas reservoirs has gradually become more and more important in Sichuan Basin.In the background of international oil prices continued to fall,how to develop horizontal well of Changning block in low cost and improve the quality of shale drilling rate,has become an urgent problem to be solved.We investigate the general geological situation of Changning block first.Based on the understanding of structure and strata situation,we make stratigraphic correlation and select the target layers of horizontal well.And then introduce the principles of LWD gamma parameter and element logging of cuttings in geosteering.We summarize the geosteering technology with low cost,and achieved very good results in the Changning area.Finally,we predict the grosteering technology with low cost will have a very important application in the future construction of lower Silurian strata mainly.In this paper,the following results are obtained:1、Longmaxi formation is divided into two sections,and S11 is subdivided into 1 sub section and a 2 sub section,then S111 is divided into 4 layers.We select the O3W2,S1111-1 and S111-2 as grosteering target of horizontal well development.2、As the main parameter of geosteering in the shale gas,the logging while drilling gamma parameters can effectively identify the S1111-1 and S1111-3,and distinguish them from the S1111-2 and S1111-4。3、Gamma ray spectrum of cutting is consistent with the LWD curve and can be used as an effective supplement with the LWD curve.They can reflect each other.When the LWD curve is abnormal,the problem can be found and solved timely through Gamma ray spectrum curve.4、By element logging of cuttings,we can effectively distinguish the different layers of shale through the curves of aluminum,potassium,iron and calcium,especially for the S1111-2 and S1111-4 which are not easy to distinguish using single gamma parameter.To a certain extent,this method can help to determine whether the trajectory is up or down in target layer,so it is very helpful for the geosteering.5、Seismic resolution has some limitations for thin reservoir identification,but seismic profile of depth domain has a certain role in predicting dip angle,and can be used as an auxiliary method of geosteering./6、The geosteering technology of LWD gamma parameter combining with Gamma ray spectrum and element logging is formed.The application of this technology in the development of Changning area is good,which can effectively reduce the cost of single well development.By the end of 2016,the low-cost geosteering technology had been successful in fifty-four wells of more than 8 Shale gas platforms,and the drilling rate of the target is above 95%.