This paper was prepared for presentation at the 1998 SPE European Petroleum Conference held in The Hague, The Netherlands, 20-22 October 1998.
Gravel-packing of open-hole highly-deviated or horizontal wells is increasingly becoming a common practice, especially in deep water and sub-sea completion environments where production rates may reach up to 50,000 BOPD or 250 MMSCFD. In these wells, reliability of the sand face completion, in addition to other factors, is of utmost importance due to the prohibitively high cost of intervention or side-tracking and the very high hydrocarbon recoveries required per well. To date the norm in gravel-packing such wells is water-packing or shunt-packing with water-based fluids. With both techniques, filter-cake removal treatments are conventionally done through coiled tubing after gravel packing, pulling out of the hole with the service tool and running in with the production/injection tubing. Furthermore, because conventional gravel-pack carrier fluids are water-based (brine or viscous fluids), water-based drilling fluids are traditionally used to drill the reservoir section to ensure compatibility and improve wellbore cleanup, even if the upper hole is drilled with a synthetic/oil-based drilling fluid. In this paper, we discuss several novel techniques that can substantially improve return on investment in gravel packing of open-hole horizontal completions, through reduced cost and process time, improved fluid management practices, increased productivity and/or reduced risk of future interventions, so mitigating against the risk of sand face completion failure or under-performance. The proposed techniques include:Simultaneous gravel-packing and filter-cake removal with water-based carrier fluids when the reservoir is drilled with a water-based drilling fluid: laboratory data relevant to gravel-packing are given and field case histories are discussed in detail.Simultaneous gravel-packing and cake cleanup with either water or a synthetic/oil-based carrier fluid when the reservoir is drilled with a synthetic/oil-based drilling fluid: laboratory data on cake removal while gravel packing are presented for both water-based and oil-based carrier fluids along with data on kinetics of cake removal.a new service tool that utilizes wash-pipe as continuous tubing and thus allows spotting of breaker treatments immediately after gravel packing: detailed description of the tool and its operation is given.Gravel-packing of highly-deviated or horizontal wells above fracturing pressure. Benefits offered by each of the proposed techniques are discussed in detail along with their current limitations. Introduction A great majority of the highly-deviated and horizontal wells are being completed as open holes, primarily because of their much higher damage tolerance, higher well productivities at high mobilities (kh/µ) and lower cost compared to cased holes. Although most of these wells in areas requiring sand control have been completed with standalone screens, a rapidly increasing fraction of them are now being gravel packed, particularly in deep water, high production rate and/or sub-sea completion environments (currently ca. 40%, and projected to be ca. 60% by 2003/2004). The major drivers for this current trend are the prohibitively high cost of intervention and much higher reliability associated with gravel packs.1,2
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn this paper, we present a novel approach for drilling and completing open hole horizontal wells with a fully compatible synthetic/oil-based fluid system utilizing shunt tube technology. The proposed RDF is a synthetic/oil-external emulsion that is reversible through exposure to a fluid of pH less than 7. A surfactant package included in the RDF waterwets the bridging/weighting agents (e.g., CaCO 3 ) upon reversal of the emulsion. The synthetic/oil external emulsion developed for gravel packing typically contains 50-75% by volume aqueous phase as the internal phase and is completely solids-free. The internal phase can either be brine or a pHreducer as well as a fit for purpose dissolver for the bridging agents. The pH-reducing property of the internal phase provides the required break mechanism for the S/OB-RDF emulsion remaining in the RDF filtercake under leakoff conditions allowing the bridging agents and drill solids to be water-wet, ensuring dissolution of the bridging agents.Laboratory data are provided for filtercake removal kinetics as a function of temperature, overbalance during gravel packing, gravel mesh size, and drill solids concentration in the RDF. Rheological data are given. Retained permeabilities and flow initiation pressures measured with the combined core and gravel-pack system are presented. Implications of the laboratory results on field practice are discussed.
Summary Openhole sand-control technique selection has been a topic of interest since the late 1990s and was discussed most comprehensively in SPE 85504 (Price-Smith et al. 2003), which proposed guidelines for selection between standalone screens (SASs), α/β packing, and shunt-tube packing. Proposed guidelines were based on formation characteristics such as formation strength, particle-size distribution (PSD), mineralogy across the well path; risk factors involved in execution as well as reliability/longevity; and cost considerations. From a PSD standpoint, their guidelines were based on the criteria proposed earlier in SPE 39437 (Tiffin et al. 1998), whereas risk evaluation was based on the technologies available at that time. Since then, significant advancements were made in understanding sand-retention mechanisms and failure modes of SASs, and in technology development to extend the limits of openhole gravel packing. These combined with the field experience in the last decade certainly warrant re-examination of their guidelines, which is the objective of this paper. In this paper, we begin with a critical review of the current sand-control technique-selection methodologies for openhole completions, including the way some of the risk factors are being evaluated to eliminate a given completion technique. On the basis of the technologies developed in the last decade, we propose a new approach for selecting sand-control technique, along with techniques/tools for proper evaluation of the risk factors. The proposed approach significantly extends the application limits of SASs and α/β packing compared with what was proposed in SPE 85504 (Price-Smith et al. 2003).
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