Research On Logging Geosteering Technology Of Shale Gas Horizontal Wells In Southern Sichuan

Shale gas with a great thickness is widely distributed in China, but it is buried deeply with a complex formation background. With the complex lithology, hard brittle rock, small porosity, complex structure and very low permeability, shale gas reservoir has strong heterogeneity and anisotropy, which greatly increases the difficulty of the shale gas exploration and development. Currently, the exploration of shale gas in the south of Sichuan province has become the key area of shale gas exploration and development in China.Drilling practices in the two major oil companies in the south of Sichuan province indicate that the most of shale gas horizontal wells not only have long period of drilling, and the rate of Sweets(High quality reservoir) drilled is as low as the ratio of input-output. Based on the study of geosteering applications at home and abroad, and combined with the characteristics of the shale gas reservoir and field data, this paper aims to carry out the research on the logging while drilling data interpretation and geosteering technology of shale gas horizontal well. Main results can be drawn in this paper from the following four aspects:(1) According to the characteristics of Longmaxi formation and Qiongzhusi shale gas reservoirs in the study area, on the basic of comparison and analysis of the logging while drilling and wireline well logs, this paper analyzes the main affecting environment factors of the well logs; Based on the environmental impact correction charts of Schlumberger, the paper establishes the curves correction model and program modules which are applicable in the study area of shale gas, and achieves the automatic correction of gamma, neutron, density and resistivity, and providing guarantee for the fine interpretation of logging while drilling..(2) Combined with core data of experiment analysis, the paper has established the interpretation models of physical parameters, gas source parameters, mechanical parameters and brittleness index while drilling in shale formation, and formed the meticulous interpretation method and related procedures of the shale formation parameters while drilling. Through analyzing the logging response characteristics of shale reservoir, and optimizing the feature parameters (Gamma, neutron, density, resistivity, organic carbon content and brittleness index) of reservoir sweet, the author adopts the method of two multi-parameter vector identification to identify high-quality shale gas reservoir, and providing the target direction for geosteering.(3) Through the comparison and analysis of adjacent well logging data, the target layer and the guide mark layer of the study area are determined, this paper also has set up geosteering model of the target zone layer with logging; according to rock physical properties of undrilled formation, the author has established the leading model curves of geosteering with logging, and proposed the Leading log response characteristics (curves) of updating for geosteering model while drilling.(4) With the geosteering comprehensive mapping technology and combined with logging parameters, the paper studies how to determine the position of the target layer (dip,dip, etc.) and the position of the drill bit in the formation and the direction of the horizontal segment to control bit in the target layer working more effectively, As well as to correct the hole trajectory and the geosteering model curves, achieving the purpose of improving the drilling rate of high quality reservoir.Based on the above research results, a set of methods skills (software module) of logging geosteering that are suitable for the shale gas horizontal well in the south of Sichuan has been formed in this paper. According to the characteristics of Longmaxi formation and Qiongzhusi shale gas reservoirs in the study area, through study and analyzing the data of the above methods and techniques used in W201-H3 and N201-H1well etc. It can solve the problem of geological target uncertainty and high quality reservoir identification, improve the drilling rate of shale gas reservoir, and meet the requirement of shale gas horizontal well formation evaluation while drilling and geosteering.