Summary An increasing number of horizontal wells requiring sand control are being gravel packed, particularly in deepwater and/or subsea environments in which completion reliability is paramount because of the prohibitively high cost of remediation. Tophole sections in many of these wells are being drilled with oil-based (OB) fluids, with the common practice of switching to water-based fluids when the reservoir drilling starts. In the last several years, some operators started using OB drilling fluids in the reservoir section as well and gravel packed them with water-based fluids. In some cases, these practices required running predrilled liners in OB fluids and subsequently displacing to water-based fluids before running in hole with the sandface screens and gravel packing. In other instances, screens could be run in hole with OB fluids in the wellbore, and gravel packing could be performed with water-based fluids. In both cases, the presence of reactive shales and/or water-sensitive productive zones can introduce serious concern, in the event that carrier-fluid losses occur into the formation during gravel packing. Although a base-oil or diesel can be used as a carrier fluid, low density of the base oil limits such applications to low-pressure/depleted wells. In this paper, we present a case history of the first successful application of drilling and completing in an all-oil environment, using a reversible OB reservoir-drilling fluid (RDF) (the filter cake of which reverses wettability from oil to water when exposed to an acidic fluid) and an OB gravel-packing fluid. The carrier fluid used in this application included a filter-cake cleanup solution in the aqueous internal phase of the OB carrier fluid, extending the application of simultaneous gravel-packing and cake-cleanup processes that have been successfully practiced in water-based-fluid environments to OB systems. The subject application was in a high-rate gas field located offshore Trinidad, with anticipated production rates in excess of 150 MM scf/D per well. Presented in the paper is the drilling and completion selection methodology based on extensive laboratory and yard testing, along with the details of the completion and recommendations for future applications based on lessons learned. A direct comparison of the all-oil drilling and completion process to water-based drilling and completion is also presented based on a case history from the same field. Introduction Openhole gravel packing is a proven sand-control technique from both productivity and reliability standpoints and has been the preferred method of sand control by many operators in deepwater/subsea developments (Price-Smith et al. 2003; Ali et al. 2001). Synthetic/oil-based (S/OB) fluids have traditionally been the preferred drilling fluids in these environments, although the operators have often been forced to switch from S/OB mud used to drill the tophole to a water-based fluid for reservoir drilling because of various concerns, particularly in wells that will be gravel packed. The drivers for S/OB drilling have been well documented and include a higher rate of penetration, excellent shale-inhibition characteristics unmatched by any commercially available water-based fluid, gauge hole, lubrication while drilling as well as while installing sandface completion, low maintenance costs (dilution and solids-control costs in reactive silt/shale environments), and so on (Gilchrist et al. 1998). In addition, switching to an S/OB RDF is much less time consuming and simplifies fluid management at the surface (intermixing of water-based and OB fluids vs. two OB fluids, storage space on the rig, etc.).

fax 01-972-952-9435. AbstractAn increasing number of horizontal wells requiring sand control are being gravel packed, particularly in deep-water and/or sub-sea environments, where completion reliability is paramount due to prohibitively high cost of remediation. Tophole sections in many of these wells are being drilled with oilbased fluids, with the common practice of switching to waterbased fluids when the reservoir drilling starts. In the last several years, some operators started using oil-based drilling fluids in the reservoir section as well, and gravel packed them with water-based fluids. In some cases, these practices required running pre-drilled liners in oil-based fluids, and subsequently displacing to water-based fluids, prior to running in hole with the sand-face screens and gravel packing. In other instances, screens could be run in hole with oil-based fluids in the wellbore, and gravel packing could be performed with water-based fluids. In both cases, the presence of reactive shales and/or water-sensitive productive zone can introduce serious concern in the event that the carrier fluid losses occur into the formation during gravel packing. Although a base-oil or diesel can be used as a carrier fluid, low density of the base oil limits such applications to low-pressure/depleted wells.In this paper, we present a case history of the first successful application of drilling and completing in an all oil environment, utilizing a reversible oil-based reservoir drilling fluid and an oil-based gravel packing fluid. The carrier fluid used in this application included a filtercake cleanup solution in the aqueous internal phase of the oil-based carrier fluid, extending the application of simultaneous gravel packing and cake cleanup processes that have been successfully practiced in water-based fluid environments, to oil-based systems. The subject application was in a high-rate gas field located offshore Trinidad, with anticipated production rates in excess of 150 MMSCFD per well. Presented in the paper is the drilling and completion selection methodology based on extensive laboratory and yard testing, along with the details of the completion and recommendations for future applications based on lessons learned. A direct comparison of the all-oil drilling and completion process to water-based drilling and completion is also presented based on a case history from the same field.

fax 01-972-952-9435. AbstractThe Cannonball field is a one Tcf gas condensate development offshore Trinidad producing at an initial rate in excess of 800 MMcf/D from three wells. The completion design selected was 7⅝ inch production tubing with an open-hole gravel pack (OHGP). The initial well (CAN01) has produced at an initial rate of 320 MMcf/D. The calculated deliverability of this well is 415 MMcf/D. This paper discusses the completion basis of design, detailed engineering assurance of the design, qualification of critical engineered equipment, and actual results.

fax 01-972-952-9435. AbstractThe Cannonball field is a one Tcf gas condensate development offshore Trinidad producing at an initial rate in excess of 800 MMcf/D from three wells. The completion design selected was 7⅝ inch production tubing with an open-hole gravel pack (OHGP). The initial well (CAN01) has produced at an initial rate of 320 MMcf/D. The calculated deliverability of this well is 415 MMcf/D. This paper discusses the completion basis of design, detailed engineering assurance of the design, qualification of critical engineered equipment, and actual results.

Summary The Cannonball field is a one-trillion cubic ft gas-condensate development in offshore Trinidad producing at an initial rate in excess of 800 MMcf/D from three wells. The completion design selected was 7"-in. production tubing with an openhole gravel pack (OHGP). The initial well (CAN01) has produced at an initial rate of 320 MMcf/D. The calculated deliverability of this well is 415 MMcf/D. This paper discusses the completion basis of design, detailed engineering assurance of the design, qualification of critical engineered equipment, and actual results. Introduction Trinidad's gas production has increased dramatically over the past 10 years. In 1996, local gas production exceeded oil production for the first time as the twin island Caribbean state of Trinidad and Tobago moved from a predominantly oil-producing country to a major gas producer. The gas growth has been driven by an increase in local demand and construction of a liquefied natural gas (LNG) infrastructure, which now includes four trains. The company's share of the gas supply to the local market has grown from less than 350 MMcf/D in 1994 to over 2 Bcf/D by mid 2007 with production coming predominantly from several prolific gas fields located off Trinidad's east coast (Fig. 1). The Cannonball field is located approximately 35 miles off the southeast coast of Trinidad in 240 ft of water (Fig. 1). The discovery well, Ironhorse-1 ST1, was drilled in 2002. In 2005, a minimal structure (nine-slot, four-pile) production platform was installed, and three development wells were drilled and completed with a jackup-cantilever drilling rig. Initial production commenced on 12 March 2006 following pipeline hookup and commissioning. The Cannonball field was brought on production at a sustained rate in excess of 800 MMcf/D. "Trinidad's First 500 MMcf/D Well: Fact or Fiction" (Kronnah et al. 2003) discussed the Ironhorse discovery well and presented the engineering challenge of an ultrabore completion (9"-in. production tubing). The right scoping process discussed in this paper presents the various tubing sizes evaluated and articulates the decision to select 7"-in. production tubing.

No abstract