Estimation Of Gas Content And Prediction Of Pore Pressure Of Shale Gas Reservoirs

High gas content and high pore pressure are two important "dessert" characteristics of shale gas reservoirs.The gas content directly affects whether the shale gas block has industrial exploitation value,and the gas content of shale gas is mainly composed of less adsorbed gas and a large amount of free gas,so it is very important to estimate the content of adsorbed gas and free gas.Considering that pore pressure is an important factor affecting shale gas bearing,it is necessary to predict pore pressure.At the same time,in today's oil and gas exploration and development,pressure prediction also plays a key role.This paper first discusses the influencing factors of shale gas content,analyzes the relationship between each factor and shale gas content,and clarifies that TOC is the most important factor of shale gas content.Taking the Longmaxi Formation in Changning as an example,using Langmuir isotherm adsorption as the theoretical basis,using isothermal adsorption experiment data and a large number of well logs based on the data,a calculation model for Langmuir parameters in Changning area was constructed,and a calculation model for the gas content of adsorbed gas based on conventional logging data was established.The free gas content was obtained by using the water saturation and porosity according to the Lewis formula.The estimation of shale gas content was completed.Traditional formation pressure prediction methods mainly rely on the single factor of longitudinal wave velocity,ignoring the influence of other lithological parameters on pressure,and there are still large errors in quantitative prediction of formation pressure.In this paper,the elastic parameter method is used to solve the above problems,and the applicability of the Eaton method and the elastic parameter method to predict formation pressure is compared and analyzed.At the same time,the establishment of the velocity trend line under normal compaction in the Eaton method is improved by using rock physics modeling.Finally,the shale gas reservoir logging and seismic formation pressure prediction process were established,and the formation pressure prediction method suitable for Changning area was obtained.