Effect of Reservoir Properties on the Performance and Design of Gas Storage Wells

Abstract

Proposal Natural gas plays an increasingly important role as a clean energy source. The demand for natural gas changes seasonally and the desired storage reservoir should be capable of meeting the peak rates especially during the winter months. There is a need to develop more gas storage reservoirs that are managed efficiently. The inherent problem is the maximization of production with minimum cost. The maximum production is a function of gas volume controlled by the reservoir properties such as porosity, permeability and pressure. It is beneficial to determine the optimum combination of wells, cushion gas, and compression facilities to minimize the cost of developing a new gas storage reservoir or converting an existing gas or depleted oil reservoir. Many factors affect the capacity of a gas storage reservoir, and to find the best combination is a challenge. A limited improvement of formation properties can be achieved by stimulation treatments. On the other hand, decisions regarding the number, location, and type of wells, completion methods, hole size and similar decisions are the result of proper planning. In this paper, we present the results of study conducted to investigate the reservoir properties and their impact on the completion strategies for fractured gas storage reservoirs. A main goal of this study is to optimize natural gas production from fractured formations. Presented in this study are the effects of reservoir properties on the efficiency of selected well design to meet the demand. Introduction Storage of gas has received industry's attention for a long time. Optimization of gas storage field development and maximizing production rates has been investigated by several researchers.1–7 With the increased demand for natural gas as a clean energy source, many operators investigate different means of increasing performance of their field.8–10 Many design variables such as number of wells, line pressure, wellbore diameter, peak day requirements, and gathering system must be taken into account in the optimization process. Additional parameters that affect the performance of the field are formation characteristics related to geology and depositional environment. Work has been conducted to determine the optimum parameters by means of linear programming; the results are used to develop a new graphical technique.1 The resulting field design optimization graphs are given for a few limited cases, but the authors suggest the extension of graphs to any field. Furthermore, they suggest to utilize computers to generate the desired graphs with field related data. Another method using linear programming to optimize the withdrawal scheduling is also suggested.2 This approach uses the physical properties of a gas reservoir to maximize the total production during the peak season. Early planning can help to develop a gas storage field in the most efficient manner.4 As a tool, computers are used to interpret the performance of storage reservoirs and can devise optimal investment and operating parameters.7 McVey and Spivey6 presented specific procedures to determine the maximum performance of a gas storage field with minimal number of simulation runs and also minimizing the cost to satisfy the injection and production requirements. Henderson et. al.11 illustrated the use of a two-dimensional, single-phase dry gas reservoir simulator to optimize the gas storage field. They varied the location of wells to increase the production for the study area for peak demands. They found the need for additional wells from the poorer sections of the field in order to meet the highest production rates. Gouynes et. al.12 presented a case history of a storage field design optimization with a numerical model where geologic modeling was integrated into a reservoir simulation package that incorporates modeling of subsurface, wellbore, and surface gathering system flows. They found that the fully coupled reservoir characterization study was successful in improving overall field operation efficiencies. Another approach reported by researchers is the use of fracture simulation to increase production from existing reservoirs. Reeves et. al.9 studied the deliverability enhancement as a result of novel methods such as liquid carbon dioxide fracture treatment. They report work done on different gas storage fields by several operators.