A Critical Review of Completion Techniques for High-Rate Gas Wells Offshore Trinidad

Abstract

fax 01-972-952-9435.Abstract BP Trinidad and Tobago (bpTT) has been developing highrate gas fields in Trinidad & Tobago since 1999, and has six high rate gas fields currently on production, with several more in planning stages. All of the wells require sand control and this has resulted in five sandface completion types (Open Hole Gravel Pack, Cased Hole Frac Pack, Cased Hole Gravel Pack, Stand Alone Screen and Orientated Perforating). Based on the experience and field performance, open-hole gravel packing has become the preferred option. The techniques used in completing these high rate gas wells as open-hole gravel packs have included both water-packs and shunt-packs. The experiences gained from these operations have now become part of BP's open-hole gravel pack best practices.The paper details the completion evolution in BP's offshore Trinidad and Tobago high rate gas fields and the relative performance of these completion types from sand control and well productivity standpoints. Characteristics of bp Trinidad & Tobago's High-Rate Gas FieldsCurrently, there are six high rate gas fields that are being operated by bpTT in Trinidad & Tobago: Amherstia, Flamboyant, Immortelle, Kapok, Mahogany, and Cannonball. There are three other fields in the planning phase. The six producing gas fields contain multiple stacked and faultsegmented reservoirs with recoverable reserves ranging from 80 bcf to 1.5 tcf. 1 Detailed discussions of the reservoir characteristics for most of these fields can be found in several earlier publications. 2,3 The reservoirs in these fields are generally characterized as fine sand, with D 50 varying from 50 to 125 microns, uniformity coefficient (D 40 /D 90 ) of 4.5 to 15, sorting coefficient (D 10 /D 95 ) of 23 to 95, and fines content (D < 44 microns) of 14 to 47%. From a sand size distribution standpoint, based on available guidelines in the literature, gravel packing and frac packing are the preferred sand control techniques. 4,5 As of mid 2006, approximately 50 high-rate gas wells were completed in these six fields, with 10 cased and perforated (no sand control), 2 standalone screens, 8 casedhole frac-packs, 9 cased-hole gravel packs and 23 open-hole gravel packs. These completions are reviewed below, with some examples for each in detail. Additional relevant information to BP Trinidad & Tobago field developments maybe found in the literature. 6-14 Cased and Perforated (C&P) CompletionsThis technique was applied in deeper reservoirs with relatively high strength, UCS in the range of 1,600 to 2,000 psi. A total of ten C&P completions were performed in high rate gas wells, four in Amherstia, four in Flamboyant and two in Immortelle fields.