Successful Application of Oil-based Drilling Fluids in Subsea Horizontal, Gravel-Packed Wells in West Africa

Chambers, Mike; Hebert, Darrell; Shuchart, Chris E.

doi:10.2523/58743-ms

Cited by 15 publications

(22 citation statements)

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“…26 Primary reasons for this recommendation are the reliance of water-packing on cake integrity associated with lower yield stresses measured for OB-cakes compared to their WB counterparts, premature screenouts as occurred in field applications with waterpacking, 1 and successful packing and productivity results from case histories with shunt-packing. 2 This recommendation is further strengthened in low net-to-gross (e.g., < 80%) or reactive shale environments (regardless of net-to-gross) due to historically low success ratios with water-packing in such environments. 26 Thus, our discussion will focus on the selection of a carrier fluid with the premise that shunt-packing will be the placement technique.…”

Section: Discussion Of Fluid Options and Recommendationsmentioning

confidence: 99%

“…[1][2][3] In all three cases, displacement from an OB to a WB fluid was done prior to running the sandface completion assembly into the hole.…”

Section: Gravel-packing With Water-based Carrier Fluidsmentioning

confidence: 99%

“…2 In these applications, the horizontal open hole section was displaced to an HEC solution and the cased hole to completion brine prior to running in hole with sand control screens. Gravel packing of the horizontal section with excess over gauge hole volume was then achieved in all three completions (i.e., 100% pack efficiency), despite complete losses throughout the operation in two of these wells.…”

Section: Gravel-packing With Water-based Carrier Fluidsmentioning

confidence: 99%

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Use of Oil-Based Reservoir Drilling Fluids in Open-Hole Horizontal Gravel-Packed Completions: Damage Mechanisms and How to Avoid Them

et al. 2001

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Open-hole horizontal wells are increasingly used to improve reservoir exploitation and production rates by targeting specific zones and maximizing reservoir exposure. The drilling fluid of choice in many of these wells is "oil based" due to enhanced drilling rates with minimized friction as well as improved wellbore stability. However, in horizontal wells requiring gravel packs, the industry in general has been reluctant to use OB reservoir drilling fluids (RDF) for various reasons. Because the gravel pack (GP) carrier fluids that have been successfully used to date are all water-based and the use of OB-RDF would necessitate displacement of open hole to WB fluids prior to GP, the practice has been to switch to WB-RDF once in the reservoir section. This was due to concerns as to adverse fluid-fluid interactions resulting in sludging and difficulty in maintaining filtercake integrity while displacing OB-RDF in the open hole, leading to complex fluid management issues. An additional factor has been the perception that WB-RDF filtercakes are easier to remove should it be necessary, since most commonly used cleanup chemicals are water-based and the weighting/bridging agents used in the RDF are also water-wet if the RDF is water-based. In this paper, we present results from experiments conducted with OB-RDFs in the presence of gravel packs. We investigate two scenarios:the gravel pack carrier fluid is water-based, andthe gravel-pack carrier fluid is oil-based. In the first case, provided that no sludges are formed during displacement to water-based fluids, the retained permeabilities are comparable to or better than those obtained with WB-RDFs, although values lower than 0.04% can be expected in the presence of sludging. Another issue relevant to gravel packing wells drilled with OB-RDFs is the yield strength of their filtercakes in comparison to WB-RDFs. It is found through yield stress measurements of various RDF cakes that OB-RDFs have several orders of magnitude lower yield strength than their WB counterparts. This finding is consistent with the reported lower flow initiation pressures for OB-RDFs, and indicates that cake erosion during gravel packing is more likely with OB-RDFs. In order to optimize the sequence of fluids to obtain a good displacement of the RDF at field scale, we use a purpose-built numerical simulator. This simulator is a fluids mechanics code that can accurately calculate displacement fronts in field conditions: eccentric deviated annulus with as many fluids as necessary. Its main use is to detect unstable displacements such as channeling of the displacing fluid on the wide side of the annulus or slumping in horizontal portions. Furthermore, we provide data on a new oil-based gravel pack carrier fluid that can be used to eliminate fluid incompatibility and fluid management issues associated with the switch from OB to WB fluids. The laboratory and large-scale yard test results are presented, addressing critical considerations for oil-based GP carrier fluids. It is found that such emulsion systems can thicken or break (depending on the emulsifier concentration) at high shear rates unless the emulsion is made at the highest shear that it will be exposed to. The implications of these results on field practices are discussed along with recommendations on avoiding damage in gravel packed wells drilled with oil-based RDFs.

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Section: Discussion Of Fluid Options and Recommendationsmentioning

confidence: 99%

“…[1][2][3] In all three cases, displacement from an OB to a WB fluid was done prior to running the sandface completion assembly into the hole.…”

Section: Gravel-packing With Water-based Carrier Fluidsmentioning

confidence: 99%

Section: Gravel-packing With Water-based Carrier Fluidsmentioning

confidence: 99%

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Use of Oil-Based Reservoir Drilling Fluids in Open-Hole Horizontal Gravel-Packed Completions: Damage Mechanisms and How to Avoid Them

et al. 2001

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“…Parlar et al (2004) discuss the major risk associated with wellbore instability, particularly with shaly intervals. Chambers et al (2000) discuss possible fluid loss associated with contact with the filter cake. Some operators prefer conditioning the NAF that was used to drill to TD (Barry et al 2012).…”

Section: Introductionmentioning

confidence: 99%

A 20/80 Oil/Water Ratio Nonaqueous Screen Running System Successfully Employed In Equatorial Guinea

et al. 2013

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An innovative surfactant chemistry in a nonaqueous system with an oil-to-water ratio (OWR) of 20/80 was effectively utilized for the first time to provide wellbore stability and run a sand-control screen in an openhole gravelpack completion. This novel type of invert emulsion system uses relatively higher aqueous internal phase, i.e., less than 50/50 OWR, which subsequently allows for a relatively higher density than the drilling fluid. More importantly this system is maintained as solids free and oil continuous.The increasing application of Inflow Control Devices/Intelligent Wellbore Systems and swellable elastomers as well as drilling longer intervals and their exposure to shale/sand dictates the use of compatible and solids-reduced invert systems to reduce the risk of an unsuccessful gravel placement treatment caused by shale swelling or plugging of sand control screens. This novel high-internal phase system provides flexibility for these types of completions. The use of the higher internal phase allows the formulation of oil-continuous solids-free systems while still achieving the required density necessary in solidsladen aqueous systems. This paper will focus on the selection of the 20/80 high-internal-phase system for this openhole completion, the upfront testing and planning for deployment. Discussion will also be provided with respect to the mixing of the system at the wellsite as well as the lessons learned.

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“…Ideally, removal of oil-based mud cake should be done immediately after well completion to avoid long-term mud and solids aggregation in the wellbore. Residual mud cakes after wellbore displacement with solids-free OBM DIF are relatively thinner and easier to remove at low drawdown pressure during initial production phase 1,2 . Nevertheless, in many other conditions, wellbore cleanup with the reactive treatment fluids is required for filter cake dissolution and removal.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Nonreactive Aqueous Spacer Fluids for Oil-based Mud Displacement in Open Hole Horizontal Wells

et al. 2012

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Reactive mud cake breaker fluids in long open hole horizontal wells located across high permeability sandstone reservoirs has had limited success because they often induce massive fluid losses. The fluid losses are controlled with special pills, polymers and brine or water, causing well impairment that is difficult to remove when oil-based mud (OBM) drill-in fluids (DIFs) are used. This situation has resulted in the drive for an alternative cleanup fluid system that is focused on preventing excessive fluid leak off, maximizing the OBM displacement efficiency and allowing partial dispersion of the mud cake for ease of its removal during initial well production. The two-stage spacer application is composed of a nonreactive fluid system, which includes a viscous pill with nonionic surfactants, gel pill, completion brine and a solvent.Extensive laboratory evaluation was conducted at simulated reservoir conditions to evaluate the effectiveness of the OBM displacement fluid system. The study included dynamic high-pressure/high temperature (HP/HT) filter press tests and coreflood tests in addition to wettability alteration, interfacial tension and fluid compatibility tests.The spacer fluid parameters were optimized based on wellbore fluid hydraulic simulation and laboratory test results, which indicated minimal fluid leak off and a low risk of emulsion formation damage. Three well trials were conducted in a major offshore field sandstone reservoir drilled with OBM. All three trial wells (one single and two dual laterals), which were treated, have demonstrated improvement in production performance. This paper will discuss in detail the spacer fluids optimization process, laboratory work conducted and the successful field treatments performed.

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Successful Application of Oil-based Drilling Fluids in Subsea Horizontal, Gravel-Packed Wells in West Africa

Cited by 15 publications

References 0 publications

Use of Oil-Based Reservoir Drilling Fluids in Open-Hole Horizontal Gravel-Packed Completions: Damage Mechanisms and How to Avoid Them

Use of Oil-Based Reservoir Drilling Fluids in Open-Hole Horizontal Gravel-Packed Completions: Damage Mechanisms and How to Avoid Them

A 20/80 Oil/Water Ratio Nonaqueous Screen Running System Successfully Employed In Equatorial Guinea

Evaluation of Nonreactive Aqueous Spacer Fluids for Oil-based Mud Displacement in Open Hole Horizontal Wells

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