A Predictive Model Enhances Optimized Production and the Completion of the Production System

ABSTRACT A gas or an oil production system is usually composed of several distinct elements, one of which can be characterized as "flow through the well completion section with the pressure drop from the sandface flowing pressure to the bottomhole flowing pressure". This segment consists of fluid flow through different types of completions such as openhole completion, perforated and gravel-packed or conventionally perforated tunnels that are not gravel-packed. The prediction performance, the production optimization and the productivity of a gas or an oil well is strongly affected by a composite or total skin around the completion zone. In perforated completions, the completion interval consists of the perforation tunnels extending from the inside casing wall through the casing and cement sheath to a point within the sandface near the wellbore. A principal factor in the design of a well completion is the consolidation or competency of a producing formation. If the completion is a gravel pack, as in the case of poorly or unconsolidated sands, perforation tunnels should be gravel-filled to a point outside the cement sheath or perhaps up to the cement sheath-sandface interface. In non-gravel packed perforated completions, as in the case of highly consolidated or competent formations, the perforation tunnels are probably unobstructed and extend to a point within the sandface. A thin zone of compacted formation surrounds each perforation tunnel creating a "skin effect" due to perforation damage. The objective of this paper is to show that the economic development and production of gas or oil wells dictates consideration of two separate but related subjects: Total optimization of the production systemLimitation of pressure drop through gravel packed or conventionally perforated completions that are not gravel-packed. This paper will show that the maximum production rates possible from gas wells are usually restricted by limiting design parameters. Proper evaluation of these critical areas can extend the life of the a well six to seven-fold. Although this paper is addressed specifically to gas wells, the techniques shown can be applied to oil wells as well as any other gas production system.