A quick and reliable production prediction approach for multilateral wells in natural gas hydrate: Methodology and case study

Multilateral well is a promising solution to increase natural gas hydrate (NGH) production. To simplify the production prediction of multilateral wells in NGH, this paper proposes a meshless method. The moving boundary divides the hydrate reservoir into an expanded dissociated region and an original formation. The Laplace transform and the Stehfest inversion method are used to obtain the solution of dual-porosity media in the dissociated region and the outer original formation with different flow abilities. The superposition principle is chosen to handle the interference effect among various branches. A numerical verification in the commercial simulator is performed. The case study from Shenhu area and the sensitivity analysis show that the production behaviors can be divided into three stages. The first stage of rapid production decline is controlled by the structure of multilateral wells. The second stage reflects the gas flow from matrix to natural fractures in the dissociated region and the dissociation of hydrate to natural gas in the original formation. The third stage is mainly affected by the original reservoir properties and hydrate decomposition. Since the proposed method does not require mesh generation, it has advantages in computational performance and convergence compared with traditional numerical techniques.