Completion Design Using Sand Management Approach Based on Sanding Prediction Analysis for HPHT Gas Wells
Authors: Fuh Giin-Fa , Nozaki Manabu 
Published: October 2014

This paper outlines our selection of well completion design based on the results of sand production prediction for each of the development wells and the total sand production to be expected from the field. The methodology on the formation failure and modeling analysis for sand production and sand rate prediction is provided for the HPHT gas and gas condensate field located offshore in the UK's Central North Sea. Sand production caused by the failure of reservoir formations through pressure depletion and drawdown pressure could lead to a significant loss in well production, well/facility damage or ultimately total well failure. The key objective of this evaluation and sand rate prediction analysis was to develop a well completion design that will deliver effective sand control throughout the producing life of the field.

Over the field life it is both critical and prudent to predict the sanding potential of a given reservoir during continuous well production for any completion design under consideration. This paper illustrates our comprehensive geomechanics investigation for sanding potential and sand rate prediction analysis for all the planned wells to be drilled and completed in the very thick sandstone reservoirs. We'll also show that if the reservoir rock strength and its variability along depth are properly measured for each well (through well core testing and log data analysis), the conditions that induce sand production issues for each specific interval could be predicted. In addition, the most important factors contributing to sanding problems have been identified to be the rock strength, flowing bottom-hole pressure, reservoir pressure, in-situ stresses, and flow rate. Therefore if permeability distribution and oil/gas and water saturations were measured (for each well) in addition to the reservoir rock strength, the optimal completion method to reduce the likelihood of sand production problems without significantly impacting production could be found. A 3D non-linear elastic-plastic finite element model incorporated with a fluid-flow module (reservoir component) has been effectively used to conduct such analysis. The key findings from this investigation can be summarized as follows:

The sand production rates based on the planned reservoir depletion and production schedules are predicted for each of the eight wells as planned for the field development; We can further update the original sand rate prediction model using the new rock strength and permeability/porosity test results obtained from the immediate testing of the new well cores as retrieved from one of the early development wells; The predicted sand rates in both daily and total sand production are low enough to warrant our sand management (rather than sand exclusion) approach to this new field; and The sand prediction results enable us to come up with optimal well platform/facility design to cope with the predicted sand rates to be produced throughout the reservoir life. The production engineers can also make sure that the overall safety of the facility is to be achieved by conducting regular and periodic inspections of any likely sand erosion for the surface chokes or pipes in the wells that especially have been forecast to produce more prolifically with relatively higher sand rates.