Study On Numerical Simulation Of Dual Laterolog Using Finite Element Method In Shale Gas Reservoir

Shale gas is a very important kind of unconventional energy, and plays an important role in ensuring energy security of our country. Shale gas reservoir is abundant in China, and mainly distributes in the southern region of marine shale. Due to the complex southern surface condition and geological condition, the effect of conventional seismic exploration method is not ideal. One of the important parameters of reservoir evaluation is resistivity, and electrical logging is able to detect difference in formation resistivity, so it is an important tool in oil and gas exploration. Dual laterolog is a kind of electrical logging method with shallow lateral and deep lateral work modes. This method is to measure the apparent resistivity with two modes, and uses forward modeling and inversion technique to study the shale gas reservoir distribution characteristics.This thesis begins with a brief introduction to the basic principles and current development of the dual laterolog, deduced variational problems from stable current field, and then use C/C++ language to implement the dual laterolog finite element numerical simulation program. In the process of solving finite element linear equations, preconditioning conjugate gradient algorithm was adopted. And according to the features of preconditioning conjugate gradient algorithm, the GPU parallel optimization was realized on CUDA platform, and greatly improved speed of the program. Finally the effect of different formation models on the response of dual laterolog forward modeling was studied.On the basis of summarizing the predecessors’ information, different shale gas reservoir models were set up, and analyzed the impact on the dual laterolog response of different parameters, such as the caliper, invaded zone, mud, formation thickness. The results show that resolution of dual laterolog for stratigraphic thickness greater than 1m is better. When the borehole diameter is greater than 0.4m, shallow lateral simulation results can’t reflect the features of layer. And when the invasion depth is greater than 1m, dual laterolog can’t reflect the characteristics of the formation. Finally, according to the characters of shale reservoir in Sichuan region, a multi-layered carbonaceous shale reservoir model was established. The research has shown that dual laterolog can distinguish low resistance carbonaceous shale thin layers, and can identify multiple sets of shale gas reservoir.