摘要
Thin carbonate reservoirs with low permeability and porosity are widely distributed in the Sichuan Basin.Horizontal drilling can maximize the volume of these thin reservoirs in contact with wellbore,thus improve single well productivity.However,how to keep the horizontal well trajectory going within the thin reservoirs is a big challenge to geosteering.During the drilling of the first geosteering well M-24 targeting the payzone of the needle-like dolomite reservoir T2l11 in the Middle Triassic Fm,Sichuan Basin,reservoir discrimination had to mainly rely on logging parameters and the logging while drilling(LWD)could only provide Gamma ray data,so it is necessary to perform studies on the LWD evaluation method.Composite logging parameters were studied first to select multiple parameters including cutting logging,drilling time logging,mud logging and Gamma ray as effective basis of reservoir identification.Based on the real-time accurate identification of the lithologies of strata as well as the real drilling data(drilling time and Gamma ray),reservoirs can be identified and divided.During evaluation while drilling,the logging interpretation can be used to guide real time geosteering and help keep the horizontal well trajectory going within the thin reservoirs.A comparison of the results of evaluation while drilling with the post-drilling logging interpretation reveals that they are basically the same,verifying the practicality and accuracy of the LWD evaluation methods.