Theoretical Study On Modern Production Decline Analysis Methods For Shale Gas Wells

Shale gas, a growing hot spot and focus in oil and gas exploration and development field, is usually accompanied with more particularity and complexity than its conventional counterparts in reservoir characteristics, transport mechanism and project peculiarity. Whereas, due to the deficiency of the relevant models and analysis tools, current advanced production decline analysis theory and method is relatively undeveloped for shale gas performance description, analysis and prediction.To solve these problems, this paper conducts an in-depth study and thus makes major achivements as followings:(1)Based on both domestic and international literature review, via deep analysis on reservoir characteristics together with transport mechanisms, this paper treats shale gas movement as two joint flows associated by a moving boundary. And on the basis of the apparent permeability concept, a gas flow model concerning surface diffusion, adsorption as well as slippage effect, which holds in the whole Knudsen number range, is eatablished in the aid of equivalent flow resistance method. Besides, the influence of some parameters like pressure and pore radii on shale gas permeability is discussed.(2)With the introduction of shale gas permeability model product obtained in (1), this paper builds up Extended Composite Linear Flow Model. It is a transient seepage flow mathematical model for multi-stage fractured horizontal well in a rectangular shale gas reservoir, considering simultaneously SRV, desorption, slippage and diffusion. The analytical expressions of both dimensionless bottomhole pressure and rate response is obtained with a series of mathematic methods during solving this problem.(3)The long-time asymtopic approximations of those dimensionless response results mentioned in (2) is realized as a consequence of asymtopic analysis. Next, re-modeling as well as re-solution with a customized set of parameters yields the production responses normalized in the late time.(4)Fetkovich typecurves and Blasingame rate-time typecurves, the two most typical as well as representative ones among advanced production decline methods, is drawn in the aid of Stehfest numerical inversion procedure programmed on Matlab platform. And the sensitivity of curves to the influencing parameters is discussed.(5)A field case in utilization proves the validity of the theory and the feasibility of the method proposed in this paper.The research results of this paper are of theoretical and practical value for shale gas production decline analysis. Hence, this work can be a useful reference to shale gas exploration and development.