Scheduling Gas Field Production for Maximum Profit

A mathematical procedure for finding the most profitable gas field production policy to meet a gas profitable gas field production policy to meet a gas sales contract has been developed. Results indicate profits can be increased through combinations of profits can be increased through combinations of earlier liquids production, increased gas recovery, and investment reduction. The optimal plan for operating a gas field is found by applying nonlinear programming to the over-all problem o production programming to the over-all problem o production rate scheduling. Risk is accounted for by specifying that any investment yield some minimum incremental profit-to-investment ratio. Computed results, an profit-to-investment ratio. Computed results, an illustrated by several example problems, include average and peak production rate schedules for each reservoir, well-drilling schedules in each reservoirs, a list of recompletions, and compression purchases for the field. Compression can be assigned purchases for the field. Compression can be assigned to each reservoir or it can be pooled in the field. Dynamic programming is used to find the best investment schedule in each reservoir. Each gas reservoir is assumed to have a uniform pressure distribution throughout. Water influx is described by the van Everdingen-Hurst analytic solution for a radial aquifer. In each reservoir, one set of gas-well deliverability curves for production to four delivery pressures is employed, and in-place facilities are always operated to minimize compression requirements. The Single-Reservoir Problem We shall solve the following optimization problem for a single gas reservoir: Given a desired gas delivery schedule and a specified peak delivery capability, find the optimal schedule for drilling new wells, the optimal plan for installing compressor horsepower, a detailed operating plan, and the total discounted profit for the best policy. We make the following assumptions in the analysis. 1. Pressure is uniform throughout the reservoir. This implies that well location is immaterial. 2. A single set of well deliverability curves is adequate. 3. The unsteady-state water influx equations satisfactorily describe aquifer behavior. 4. The optimum policy can be broken into two stages. In the first period, desired peak delivery capability is maintained through the addition of wells and compressive horsepower In the second period no new wells are drilled and no compression period no new wells are drilled and no compression is added; the reservoir flow rate declines.