Research On Parameter Characterization Of Shale Reservoirs By Well Logging Interpretation

Shale oil and gas resources have been regarded as one of the most important unconventional resources.Shale reservoirs are different from conventional reservoirs,due to their distinct characteristics of lithology and reservoir types.Well logging interpretation and evaluation still cannot be satisfied the requirements of the oil and gas exploration and development in shale reservoirs.Parameter characterization of shale reservoirs by well logging interpretation is still weak and challengable.Hence,it is an urgent need to implement studies on log-response mechanisms and improve interpretation and evaluation technology for shale reservoirs.Taking Longmaxi shale as the main research object,the parameter characterization of shale reservoirs is carried out based on the shale outcrop,core analysis data,logging data,and so on.This study aimed to improve the accuracy of the calculated parameters for shale reservoirs using conventional logging data.First,the log-response characteristics and the sensibility of key parameters of shale reservoirs were investigated.The porosity and mineral composition contents were predicted using a radial basis function neural network(RBFNN).Then,the log-response characteristics and the sensibility for total organic carbon(TOC)content were analyzed,and a new method named logging curve separation method was proposed for TOC estimation.The calculated results agreed well with TOC measurements from core.Tough conventional water saturation models were not applicable in shale reservoirs.they had a good relationship with TOC and core water saturation,and two new methods were proposed for the calculation of water saturation in shale reservoirs,and named as TOC revised water saturation method and water saturation-difference method,respectively.Archie formula and modified total shale formula were researched using these two new methods,and the estimated results are in good agreement with the core water saturation.After that,the relationships of gas content with water saturation and brittle mineral content are studied.It is demonstrated that the gas content has non-linear relations with water saturation,which is based on Archie formula after TOC revision,and brittle mineral contents.Two different calculation models of gas content(adsorbed gas content)are established,and named as water saturation method and brittle mineral content method,respectively.Finally,the relationships among important parameters of shale reservoirs are investigated,and a comprehensive evaluation indicator for the shale quantification is established.Through this study,a set of credible parameter evaluation methods,which can be technical supports for the exploration and development of shale reservoirs,are established.