阵列感应测井在廊固凹陷W10断块沙四下储层中的侵入特征

Mud Invasion Characteristics of Array Induction Logging from the E_(S_4)~X Reservoirs in W10 Block,Langgu Sag

阵列感应测井电阻率能够很好地识别泥浆滤液侵入引起的地层径向电阻率变化。廊固凹陷W10断块沙四下储层阵列感应电阻率不仅存在正差异,还出现了高电阻率环带和低电阻率环带特征。根据泥浆的侵入机理,分析泥浆的侵入特点,利用阿尔奇公式对孔隙度、含水饱和度、矿化度变化对电阻率影响进行数值模拟,将电阻率变化归纳为泥浆滤液的驱替作用和扩散作用,认为在淡水泥浆钻井条件下,驱替作用使地层电阻率降低,扩散作用使地层电阻率增大。在此基础上分析泥浆侵入引起高电阻率环带和低电阻率环带原因,淡水泥浆侵入,泥浆滤液电阻率大于地层水电阻率;泥浆渗透速度与油水相的渗透速度关系,大于时则会形成高电阻率环带,反之,小于时在未侵入带之前形成含水饱和度相对较高的低电阻率环带。用差异累计法识别不同阵列感应电阻率特征所代表的流体类型,实例表明该方法应用效果较好。

The array induction log can easily identify the radial variation of the formation resistivity during the mud invasion process.In the E_(S_4)~X reservoirs in Wu10 block of Langgu sag,the induction resistivity not only displays positive separation feature,but also low resistivity annulus and high resistivity annulus.Based on the mechanism of the mud invasion,we analyze the characteristics of mud invasion,and the Archie equation is used to simulate the characteristics of the resistivity when the porosity,water saturation,formation water salinity are changed.The result can be generalized as the mud filtrate displacement contribution and diffusion contribution.While drilling with the fresh mud,the displacement contribution causes the resistivity decrease,the diffusion contribution causes the resistivity increase.And then we analyse the reason of the high resistivity annulus and the low resistivity annulus which are caused by the mud invasion.Because the mud filtration resistivity is larger than the water resistivity at the process of drilling with fresh mud;it is subject to the relative magnitude between the mud infiltration velocity and the oil-water two-phase infiltration velocity.If the first one is larger,the high resistivity annulus is developed,on the contrary,it will develop a low resistivity annulus where the water saturation is more higher before the non-invaded zone.At last,difference accumulation method is put forward to identify the types of the fluid which are characterized by the array induction resistivity,the actual practice shows that this method has a good application effect.