Rock engineering systems adopted for sanding prediction in perforation tunnels

Abstract

Sand production is an important issue in reservoirs with weak or unconsolidated sand formations. Production of sand not only causes several problems in maintaining wellbore integrity but also is a problem during production where damages through the tubing and surface facilities are likely to occur due to the sand grains being transported along this path. The rock engineering systems (RES), initially introduced in mining and civil related geomechanics problems, is one approach to analysing the interrelationship between different parameters involved in a rock engineering project. This is the approach that was adopted in this work to study and predict the sanding potential in perforation tunnels. Sanding mechanism in perforation tunnels during production was reviewed and all effective parameters were identified. An interaction matrix was introduced to study the sanding mechanism through the interrelation between pairs of parameters. The interaction matrix was coded using a semi-quantitative rating approach to determine the interaction between each pair of parameters. The interaction intensity and dominance of each parameter in the system were studied through the cause-effect diagram to classify the parameters. This will assist in finding a better engineering action to mitigate or eliminate instabilities. A sensitivity analysis was conducted on a data set, and major parameters playing in sand production in a perforation tunnel were identified using analytical formulae. The results of sensitivity analysis were compared with the cause-effect diagram derived from the interaction matrix. A good agreement between the two methods was observed. This shows the usefulness of RES for identifying potential sanding solutions through the interaction matrix analysis.