摘要
为了明确五峰组—龙马溪组页岩“低电阻、低含气”成因,有效指导四川盆地下一步页岩气的勘探部署,依托全区大量钻井调查、解剖及分析化验测试结果,对问题开展了较为详细的研究。该区龙马溪组页岩低电阻率测井按其电性特征、地质特征的差异,可分为小于1Ω·m和1~10Ω·m两类。电阻率小于1Ω·m的页岩气井基本不含气,以干井为主,分布区域相对集中,主要位于川西南、长宁西等地区;其电阻率曲线形态具“细脖子”特征,拉曼反射率普遍在3.70%以上且出现高幅度石墨峰;另外不同状态下岩电实验电阻值变化范围小,且均呈现极低—低电阻特征,说明石墨化造成的岩石骨架导电是影响该类页岩的主要原因。页岩电阻率在1~10Ω·m范围的钻井分布区域较广,以微含气为主,在盆内、盆外均有分布,其电性、激光拉曼及岩电实验等表现出来的特征与电阻率小于1Ω·m的页岩差异明显,页岩电阻率曲线具“渐变”特征,激光拉曼实测反射率在3.50%左右,激光拉曼图谱也没有表现出明显的石墨峰特征。该类页岩进行烘干水及饱和水两种状态下的岩电实验变化范围大,即烘干前、后页岩电阻率变化在7~20倍,且呈现中—高电阻率特征,揭示页岩含水量对页岩电阻率有显著影响。结合实钻资料认为,页岩气保存条件变差、含水率增高是造成该类低阻井的主要原因。
In order to clarify the genesis of“low resistivity and low gas content”in the shale of Wufeng-Longmaxi formations and effectively guide the next step of shale gas exploration in Sichuan Basin,a detailed study on the problem based on a large number of drilling surveys,dissections,and analysis of laboratory test results in the entire area was carried out herein.Low-resistivity wells of Longmaxi Formation shale in this area can be divided into two types based on their electrical and geological characteristics,which are less than 1Ω·m and 1-10Ω·m.Shale gas wells with resistivity less than 1Ω·m are basically gas-free and mostly dry wells with relatively concentrated distribution areas,mainly located in southwestern Sichuan and western Changning.The resistivity curve of the shale exhibits a“thin neck”characteristic,with a Raman reflectance generally above 3.70%and a high amplitude graphite peak.In addition,the variation range of resistance values in rock electrical experiments under different states is small,and they all exhibit extremely low to low resistance characteristics,indicating that the conductivity of the rock skeleton caused by graphitization is the main factor affecting this type of shale.The drilling distribution area of shale with resistivity in the range of 1-10Ω·m is relatively wider,mainly with slight gas content,distributed both inside and outside the basin.The characteristics exhibited by its electrical properties,laser Raman,and rock electrical experiments are significantly different from those of shale less than 1Ω·m.The resistance curve of this type of shale exhibits a“gradual”characteristic,with a measured Raman reflectance of around 3.50%by laser Raman spectroscopy.The laser Raman spectrum also does not show obvious graphite peak characteristics.This type of shale undergoes a wide range of changes in rock electrical experiments under two states:dry water and saturated water,with a change in shale resistivity of 7 to 20 times before and after drying,and exhibits medium to high electrical resistance characteristics,revealing a significant impact of shale water content on shale resistivity.Based on actual drilling data,it is believed that the deterioration of shale gas preservation conditions and the increase in water content are the main reasons for this type of low-resistivity well.
作者
魏富彬
刘珠江
陈斐然
严伟
王强
WEI Fubin;LIU Zhujiang;CHEN Feiran;YAN Wei;WANG Qiang(SINOPEC Exploration Company,Chengdu,Sichuan 610041,China)
出处
《石油实验地质》
CAS
CSCD
北大核心
2023年第6期1089-1096,共8页
Petroleum Geology & Experiment
基金
国家自然科学基金企业创新发展联合基金(U19B6003-03-03)
中国石化科技项目群(P23070)联合资助。
关键词
低电阻率
石墨化
高含水
保存条件
页岩气
龙马溪组
川东南地区
low resistivity
graohitization
high water content
preservation condition
shale gas
Longmaxi Formation
southeastern Sichuan
