A fast forward algorithm for LWD gamma-ray response and its geosteering application

The geosteering technique is usually used in the directional or horizontal well drilling process.The key technology of geosteering is to judge the formation boundary and attitude for updating the strata model and optimizing the well path in real time,in order to maximize the reservoir-encountered rates.It is an effective method to identify the formation boundary by comparing the forward well log response simulated with a strata model with the real LWD data.Based on the attenuation law of gamma-ray(GR)in formation,this paper deduces a fast forward algorithm for LWD GR response in different strata models with the integral method,which overcomes the difficulty that the Monte Carlo algorithm is hard to be used for real-time forward calculation at present.The field application examples demonstrate that this algorithm can assist to identify the real formation boundary effectively and achieve an even better geosteering effect.