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Abstract
Gravel pack and stand-alone screens (SASs) are the two most commonly used sand-control methods for openhole (OH) well completions in unconsolidated formations. When comparing the two methods, gravel pack is considered the more robust for sand control and is expected to have a longer service life than SAS in similar reservoir and operational conditions. However, gravel pack costs more per foot than SAS, which limits its use to poorer-quality sands in projects with acceptable economics. The industry has developed accepted criteria for selecting these sand-control methods, and this documentation provides guidelines as to when SAS should be sufficient and when gravel pack is more appropriate, depending on sand quality, which is based on particle-size distribution (PSD) of formation sand samples.

Unfortunately, many small oilfields with poor quality unconsolidated formations cannot be developed economically using gravel pack. SAS is the next best alternative, and often, the only option to bring those small oilfields online. The ‘J’ Field in Malaysia is an example of a small oilfield with marginal economics that was developed successfully using SAS completions despite the fact that the sand quality called for gravel packing. This paper discusses the methodology used in selection and sizing of the SAS design for the ‘J’ Field.

The methodology involves two major processes: 1) review of PSD information for initial screen micron rating selection, and 2), retention-plugging testing of wire-wrapped screen (WWS) and mesh screens for screen-type selection and screen micron rating optimization. Using this methodology, the operator and service company were able to design a completion strategy for eleven (11) wells that fulfilled the economic needs of the development project while resolving the sand-control needs.

Introduction
The sonic log on the ‘J’ Field’s formation indicates that it contains semi-consolidated sand that is predicted to be prone to sand production, based on measurement of cut-off transit time. Moreover, the ‘J’ Field formation sands are poorly-sorted, non-uniform, and with a high percentage of fines content based on the particle-size analysis of core samples from Exploration Well-1 and Exploration Well-4, which were conducted using both dry-sieve analysis (DSA) and laser-particle-size analysis (LPSA) methods. The development plan for ‘J’ Field recommended sand control for all developmental oil wells. Sand production could be detrimental because it would impair well productivity and erode downhole and surface production equipment. Moreover, the surface production facilities were designed to allow only small-fines production.

Further review by both the operator and the service company suggested that gravel packing would be the most appropriate sand-control method for this project. This decision was based on the sand-control-method selection criteria provided in SPE 39437 (Tiffin, G., et al., 1998) using the sorting coefficient (SC), uniformity coefficient (UC), and the percentage of fines content. However, they also agreed that SAS would be the next best alternative although aware of the risk that SASs might plug early. Given the ‘J’ Field’s quantity of reserves and the cost of gravel packing, SAS appeared to be an attractive option because it would enable the economic development of ‘J’ Field. The expected skin and productivity index (PI) for SAS in ‘J’ Field in the field development plan (FDP) were 18 and 32 STB/psi, respectively.

A comprehensive study/testing program was conducted to select the appropriate type of screen and how to optimize its micron rating so that it would allow the best sand-control performance possible using SASs. Knowing that the SAS method would not equal gravel pack in terms of service life without proper design, the operator knew that proper design to maximize solids retention, and at the same time, to delay plugging was critical for success.