Study On The Optimization Strategy Of Gas Field Development Based On Product Contract Model

Integrated development of multiple gas fields is to set a group of small and medium scale gas fields that are geographical adjacent as a whole development system, produce into one common gathering or processing infrastructure. Due to the large number of gas fields, their scattered locations, and differences in capital cost and production performance, it is difficult to determine a rational startup time and productivity for each gas field directly. In order to achieve maximization economic benefit when developing an overseas multiple gas fields project, under the condition of production sharing contract mode and other physical constrains, this thesis performs research from single gas well production performance prediction to predicting multiple wells gas reservoir production performance, modelling optimization of integrated development for multiple gas fields into mathematical model, and exploring efficient solving method. The main accomplishments of this paper are as follows:(1) Based on the research result of quantitative relationship between gas offtake and plateau duration of gas reservoir, combining the material balance equation of constant volume gas reservoir with the deliverability equation of gas well, applying gas reservoir engineering theory, a quantitative model of production performance prediction in the decline period has been derived. The comprehensive application of two quantitative models in plateau and decline periods, production performance prediction in the whole production period of gas reservoir could be realized rapidly and accurately.(2) In order to achieve-maximization economic benefit of overseas oil and gas cooperative projects, analyzing the main components of production sharing contract, a net present value (NPV) objective function based on production sharing contract has been set up. Considering production needs of gas processing plant and gas field production performance constraints, a mixed integer nonlinear programming model of integrated development optimization for multiple gas fields has been established.(3) Considering the feature of the optimization model for multiple gas fields integrated development, analyzing the merits and demerits of standard genetic algorithm, a parallel-structured embedded genetic algorithm has been proposed to solve the model above in this paper. Improvement measures such as splitting the integer variables and continuous variables into two different levels, transforming fields startup time variables into fields development order, and dealing method of constraints has been put forward to reduce computational load and solving difficulty, to shorten the solution time, and to guarantee the proposed algorithm converging to global optimum.(4) Utilizing VBA language (Visual Basic for Application) to program the model preceding, and taking an overseas multiple gas fields contract block as calculation case. Three different traditional development plans have been analyzed and compared, which include all gas fields with startup in the same year, and orderly developing gas field according to the productivity of each gas field or distances between fields to gas processing plant. Results proved the necessity of performing research on the optimization of integrated development for multiple gas fields. Furthermore, the performance of standard genetic algorithm and parallel-structured embedded genetic algorithm to solve this model has been analyzed. And the optimum fields development order and productivities that maximizing the net present value have been obtained.Though the research in this article, it has been achived that production performance prediction of multiple gas fields rapidly accurately and quantitatively, and solved the challenge of orderly development for multiple gas fields. Ultimately, a technique for integrated developing multiple gas fields based on production sharing contract is formed, which provides references and assistance to develop similar small and medium multiple gas fields overseas.