Application of Waveform Indication Inversion in the Prediction of Thin Carbonate Reservoirs in the Amu Darya Right Bank Area

Abstract

The Amu Darya Right Bank Project is PetroChina’s largest onshore conventional natural gas project abroad. The project is located in the northeastern part of the Amu Darya Basin. The main target formations are carbonate formations, their overlying and underlying source rocks have entered the gas generation stage, and the conditions for hydrocarbon accumulation are very excellent. As the gas field gradually shifts from the exploration evaluation stage to the development stage, the requirements for reservoir prediction are also higher and higher. In this paper, the seismic waveform indication inversion technology has been used to perform wave impedance inversion of the 3D seismic data of the western region in the Amu Darya Right Bank Area and predict the planar distribution of thin alternate carbonate reservoirs in the target formations. Seismic waveform indication inversion is an inversion method implemented by Bayesian Discriminant theory and Markov chain Monte Carlo (MCMC) sampling algorithm. Well sample optimization is a key step in the inversion. Taking the statistical P-wave impedance as the prior information and using the information such as likelihood function, prior distribution, etc., the posterior probability distribution as the objective function is obtained under the Bayesian framework. In addition, the model parameters are constantly updated to finally maximize the objective function and obtain the final expected output result. With the seismic waveform indication inversion technology, the problems involving thin carbonate reservoirs, large horizontal difference and difficult identification of them, etc. have been overcome effectively, and the high frequency information missing in seismic data has been supplemented, thereby obtaining a good effect of high resolution prediction of thin alternate carbonate reservoirs in the area, providing a basis for evaluating favorable areas and deploying wells, and increasing the benefits of exploration and development.