Gas Field Development: Automatic Selection of Locations for New Producing Wells
Authors: Burns Pamela G. , Brons Folkert , Coats Keith H. 
Published: December 2007

Recent advancements in technology have made possible studies of gas field development programs heretofore impossible. With the use programs heretofore impossible. With the use of a mathematical model, a method for solving the simulator equations, and adequate computing equipment, various development plans can be tested and evaluated. In evaluating a development scheme, we are concerned not only with the number of wells drilled, but also when each is drilled and the cost of each well.

In order to obtain a plan for developing a gas field, there should be some criterion on which to base a decision on the location of additional wells. In this paper, we consider schemes resulting from the use of three distinct criteria. From the alternate schemes, a computer program determines the one which ultimately achieves the lowest cumulative present value cost.

The subject field of this study is a portion of the Crossfield reservoir located portion of the Crossfield reservoir located near Calgary, Alta., Canada. The flow was considered single-phase, unsteady-state, isothermal, in a closed heterogeneous reservoir with a uniform porosity. An alternating direction iterative technique was used to solve the partial differential equations in the mathematical model.

Introduction

The goal in the natural gas industry is to locate adequate amounts of deliverable reserves and to produce them efficiently. Once a gas reserve has been located and dedicated to market, there are many things that must be considered in order to produce it efficiently: The production rate on the average and maximum day is usually specified. Gas sales contracts often require that the average delivered quantity be one Mcf/D/8 MMcf of reserve. This rate depletes about 90 percent of the reserve in 20 years. The operator drills sufficient wells to ensure that he can maintain the maximum daily requirement. Well productivity is checked at intervals, and the deliverability of the field is computed to ensure that it can continue to meet the market requirement. Well reconditioning or new wells may be required at certain stages in the life. If the reservoir is producing by pressure depletion and the gas producing by pressure depletion and the gas sales contract calls for a minimum pressure for delivering gas, field compressors may be installed as the field approaches abandonment pressure. pressure. With all these considerations'. it becomes immediately evident that a plan is needed for developing the field and placing the gas on the market. Estimates of gas reserves are needed as a basis for marketing the gas. Sufficient wells must be planned to produce the gas at the rates projected for delivery of the gas.

At any stage of reservoir depletion, a correct estimation of the change in delivery capacity with time caused by depletion is essential for determining the number of wells required to meet a given contract to deliver gas. Fundamentally, the problem is the familiar one of obtaining data during the drilling, testing and early production life of a well and applying these data within a simulation model to predict long-term behavior. In planning the operation of a multiwell gas reservoir, it is desirable to predict its performance for each alternate development and producing schedule under consideration.