Abstract Predicting the production rates from a given gas well is of considerable interest in the natural gas industry. The conventional method to predict the performance of the gas reservoirs require a number performance of the gas reservoirs require a number of data which are often unavailable. This is especially true for low permeability reservoirs. In many cases, the production data is the only available information on the gas wells. In such cases, the production decline type curves have been utilized to predict the future production rate based upon the past production data. However, the published type curves production data. However, the published type curves have been generated with certain assumption(s) include consideration of only Darcy flow, use of constant gas viscosity and deviation factor, as well as ignoring the skin factor.
This paper presents a set of new production type curves for gas wells (production forecasting) without any of the above mentioned assumptions. The type curves are generated by utilizing a simple reservoir model which accounts for variations in gas deviation factor and viscosity as well as non-Darcy flow. The results of this study are presented in the form of dimensionless rate-time and cumulative production-time type curves. production-time type curves. The type curves presented in this study can be utilized to estimate the reserves and forecast future production of a given gas well. In addition, the production of a given gas well. In addition, the application of the developed type curves as found to be significantly easier than those previously published. Finally, the developed type curves were published. Finally, the developed type curves were verified using actual production data obtained from the gas wells in the Appalachian Basin.
Introduction The idea of using type curves to analyze production data was first proposed by Fetkovich production data was first proposed by Fetkovich (1980). Type curve matching as a technique, however, has had widespread application to analyze the pressure transient data for many years prior to that. pressure transient data for many years prior to that. Fundamentally, production decline type curve is a log-log plot of a family of production decline curves with dimensionless flow rate (qd) on ordinate and dimensionless time (td) on abscissa. The different curves of a family are distinguished from one another by a specified parameter. To utilize the production decline type curves to analyze the production data, first a log-log plot actual data is made. Then, the plot of actual data is overlaid on the same size type plot of actual data is overlaid on the same size type curve and a single type curve is found that most nearly has the same shape as the plot of the actual data. The matched type curve differs from the plot of actual data only by a shift in coordinates. Once a best fit has been found a match point can be selected to evaluate the dimensionless groups. Finally, the matched type curve and the dimensionless groups are utilized to estimate the future production rates.
Presently, there are several sets of production decline type curves published in literature. Some of these type curves are developed primarily for oil wells and are not directly applicable to gas wells. There are several suggested modifications to these type curves to make them applicable to gas wells. There are several suggested modifications to these type curves to make them applicable to gas wells. However, the modifications involve the use of new parameters which are difficult to evaluate and as a parameters which are difficult to evaluate and as a result complicate the matching process. On the other hand, the available gas production decline type curves are developed based on simplifying assumptions which limits their applications.
The objective of this paper is to develop a set of production decline type curves for the purpose of gas well production forecasting which are easy to use and are not developed based on simplifying assumptions.