The objective of this paper is to present an analysis and methodology to forecast individual well production in a new, developing channel sand gas reservoir complex. The paper predicts when liquid loading may occur, specifies a strategy for changing production tubing sizes, and selects the types of artificial lift that may be required in the future.
The approach of this paper is to forecast production rates using a combination of decline curves and vertical lift performance (VLP) curves. Liquid loading is projected to occur when the gas production rate of a well reaches the Turner critical flow rate in the existing production tubing size and expected wellhead pressure. Artificial lift methods are identified using an artificial lift type screening matrix based on the production parameters after liquid loading occurs. Artificial lift methods are also examined for a scenario of increased water production if water encroachment occurs in a well.
Not all wells decline at the same rate due to the nature of the sand channels. Some wells will reach a critical rate faster than others. Once a critical rate is reached in a well, the first step to maintain the flow will be to install smaller internal diameter production tubing. As production continues to decline, liquid loading will occur again in the smaller tubulars. At this point, artificial lift will be necessary to extend well life to the economic limit. The primary focus then becomes gas well deliquification using plunger lift or foam lift. For the water encroachment scenario, plunger lift or foam lift will not suffice; instead, the artificial lift methods of rod pump, gas lift, or hydraulic jet pump apply. However, a feasibility assessment will need to be made to determine whether the lift methods are economic.
This paper presents a methodology to plan for the production lifecycle of a gas field from the outset. It provides some insight on when to plan for procurement and installation of smaller internal diameter tubulars in a remote desert area where workover rigs are not present. Further, the methodology allows some assurance that artificial lift methods will be ready to implement when needed to maximize recovery.