StoSAG를 이용한 탄산염암 저류층의 유정 운영 최적화
Optimization of Well Operations in a Carbonate Reservoir Using Stochastic Simplex Approximate Gradient
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초록
유가스전 개발에 있어 유정 운영 조건은 개발 경제성에 큰 영향을 미친다. 경사도 기반의 최적화 기법을 이용하여 최적 유정 운영 조건을 효율적으로 탐색할 수 있다. 그러나 저류층 불확실성이 높고많은 유정이 존재한다면 유한차분법을 이용하여 경사도를 계산하는 데 막대한 계산량이 요구된다. 최적화 변수의 미소 변화를 추계학적으로 생성하여 경사도를 계산하는 방법 중 하나인 Stochastic Simplex Approximate Gradient(StoSAG)를 이용하면 불확실성이 높고 많은 수의 유정을 가진 유정운영 최적화 문제를 풀 수 있다. 본 연구에서는 StoSAG를 이용하여 실제 탄산염암 저류층의 생산및 주입 조건을 최적화하였다. 최적화된 운영 조건은 초기 운영 조건에 비해 순현재가치가 약 10% 증가하였다. 본 연구결과는 불확실성이 높고 유정 개수가 많은 저류층의 유정 운영 최적화를 효율적으로 수행하는 데에 활용할 수 있다.
Abstract
Well operating conditions can significantly affect the economic feasibility of developing an oil and gas field. The optimal operating conditions can be calculated using gradient-based optimization algorithms. However, using the finite difference method for this calculation is significantly costly under reservoir uncertainty and complex operating conditions. Thus, stochastic simplex approximate gradient (StoSAG), which is a calculation of the gradient by perturbing decision variables randomly, is an efficient application for optimization under uncertainty . In this study, StoSAG was applied to optimize the operating conditions in a real carbonate reservoir. Compared to the initial operating conditions, the optimized model shows a 10% increase in net present value (NPV ). The results can be utilized to determine cost-efficient operating conditions for complex reservoirs.
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