A logging interpretation method for total porosity considering organic matter correction of shale gas reservoirs

The calculation of total porosity is the key to the logging evaluation of shale gas reservoirs. On the basis of element capture,conventional log data,total porosity and the total organic carbon experimental data of AA1 well of the Wufeng-longmaxi formation in Jiaoshiba area,the applicability of Herron’s total porosity model is analyzed. The results show that the model can not accurately calculate the total porosity of the target block. The reasons are:① When calcu- lating apparent density porosity and apparent neutron porosity,the rock is equivalent to the skeleton and the pore,and the existence of organic matter is ignored. ② In the model,the weight coefficient is acquired from the least square method with limited core data,thus making it has certain regional applicability. Based on the above,an improved meth- od for evaluating the total porosity of shale gas reservoirs is proposed. Applying this method to XX1 well of the Wufeng- longmaxi formation in Jiaoshiba area,the results show that compared with Herron’s model,the accuracy of calculating the porosity of the improved model is obviously enhanced. The method is easy to be used.