Abstract

This paper presents an analytical model for predicting the sanding tendency of a gas well. predicting the sanding tendency of a gas well. The onset of sand production in a cased well may result from the failure of the perforation tunnel to withstand both the in-situ stress and the flow/production induced stresses. The failure conditions of a cylindrical perforation tunnel subject to single phase gas flow in a friable sandstone formation, have been studied using elastoplastic stress analysis. The failure criterion employed in this paper is the critical equivalent plastic strain, which is the maximum plastic strain that can be sustained without plastic strain that can be sustained without failure and consequent sand production.

The effects of various production conditions have been evaluated by considering the pore pressure distribution associated with the pressure distribution associated with the production of gas. The results demonstrate that production of gas. The results demonstrate that the flow of gas in the perforation tunnel tends to increase the instability, however compared to standard Darcy flow conditions, the inclusion of the non-Darcy flow effect due to high production rate, will significantly increase the production rate, will significantly increase the instability. The effect on stability of the tunnel geometry, rock deformation and strength have been studied to assist in the evaluation of the influence of perforation geometry, in terms of shot density and phasing, on sand instability. The results show that an optimum perforation geometry requires a compromise between the productivity ratio and cavity stability. productivity ratio and cavity stability. The results obtained by running the model against a North Sea gas reservoir demonstrate that the model is a useful tool for designing sand free production completions of alternatively assessing the sensitivity of the, sanding tendency to operational parameters.

Introduction

Sand production is a major problem in almost all fields that produce from unconsolidated or weakly cemented sandstone reservoirs. The industry has long been aware of both sand production and its associated problems and production and its associated problems and has made numerous attempts to tackle the problems with varying degrees of success. problems with varying degrees of success. The most commonly available sand control methods are listed below:

  1. Reduction of the production rate to lessthan a critical rate;

  2. Selective perforation;

  3. Gravel pack completion or other barrier approaches, eg. precoated screens etc.;

  4. Sand consolidation treatment.

The installation of any sand control technique is expensive, but it would perhaps make a well profitable where it would otherwise have been profitable where it would otherwise have been abandoned or not developed. However, the unnecessary application of such techniques as a precaution against anticipated sand production, precaution against anticipated sand production, can cause not only an increase in the production cost but also reduced productivity.

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