Sanding Assessment and Sand Control Options for a High Fine Content Unconsolidated Sandstone Reservoir, Offshore Malaysia
Authors: Khaksar A. , Younessi A. , Chatterjee A. , Ghazali I. H. , Nordin N. F. 
Published: October 2024

The target formations in the study area are high porosity, poorly consolidated gas bearing reservoirs at a depth 600-650m TVD SS. The reservoirs are fine grained sandstones with a d10 of ∼110 micron and a fines content of ∼77%. The field has been on production since 2012. All wells have been completed cased and perforated completed with active sand control consisting of gauge 6 wirewraped sand screens and 40/60 gravel. While early production wells are still producing solids-free, some of wells drilled in recent years show solids production in the form of fines with d10 of collected solids ∼27 micron and ∼100% fine content. New infill wells are planned in 2025 and a geomechanical sanding evaluation and sand control review study was conducted to identify strategies to mitigate solids production in both current and future wells. This paper highlights the findings of the sanding evaluation along with a review of current sand control systems and the root cause(s) of fines production in recent wells versus continuous solids-free production in earlier wells. The findings have provided insights and lessons learned for optimization of sand control systems in future wells and remedial options for mitigating solids production in current wells.

The sanding evaluation reveals that the recent wells have a high risk of rock failure with nearly 40% of perforations would be unstable at the onset of production. Furthermore, the severity of rock failure and hence sanding increases with depletion. In contrast, nearly 99% of the perforations in earlier wells are found to be stable and hence should produce solids free. This finding is consistent with the field observations to date. Review of sand control implemented in the wells indicates their functionality and efficiency in controlling large grain size solids. Given the very high fines content nature of the target reservoirs and their high sanding propensity, fines are expected to pass the 6g screen (avg. opening ∼150µm) and 40/60 gravel (median ∼ 335 µm). Although definite screen plugging and hot spotting had not been reported, this might still occur and cause screen failure and solids production (sand and possibly gravel) in addition to fines production in the recent wells. To reduce the severity of fines preproduction in future wells, alternative gravel sizing (e.g. 50/70) with an Extra Fine premium screen are recommended in a frac and pack completion. Geomechanics assessment suggests perforation in rocks with porosity less than 0.36 are expected to remain stable and produce sand-free for the entire well life. Fines and sand production can be further reduced by using an oriented and selective perforation strategy in future wells. For existing wells, chemical treatments for fines stabilization can be used to mitigate the fines production issues as well as through tubing erosion and plug resistant screens such as bonded bead and shape memory polymer screens as remedial sand control options.