Schlumberger

Performance Report: Equatorial Guinea: FAZEPRO Joins WARP for Successful Expandable Screen Completions

Challenge: Previous wells were drilled with a standard invert oil‐base mud (OBM) and completions involved perforations only, cased hole‐expandable woven wire screens, open hole‐expandable woven wire screens, and low‐inflow‐area woven wire screens. While good initial production was achieved, all of the previous completions resulted in either premature screen failure or unacceptable sand production. There was no displacement or treatment of the fluid prior to running in the hole with the completion assembly.

Solution: M‐I SWACO was commissioned to evaluate completion requirements and to perform the displacement and completion sequence on this operator’s wells. The FAZEPRO RDF system was recommended because of its unique reversible chemistry that combines the drilling advantages of both invert‐emulsion and water‐base systems. By adjusting the pH of either the breaker solution or the completion brine, FAZEPRO filter cake is transformed from an oil‐wet to a water‐wet state.

Result: Following laboratory tests using actual core material and simulated displacement procedures, a comprehensive drilling, displacement and completion procedure was begun. The procedure involved the use of FAZEPRO RDF and sacrificial carbonate to form a temporary bridge on the pore openings. Concentrations of acid‐insolubles (AIS) and calcium carbonate were closely monitored during drilling. Prior to screen placement, the FAZEPRO fluid was displaced to a FAZEPRO SF (solids free) fluid. With the standalone large‐inflow, woven‐wire screen in place, a displacement sequence commenced. A final acid soak was used to digest the filter cake and remove any impairment from the filter cake. To date, more than 15 wells have been drilled and completed using the FAZEPRO system and production rates are acceptable without any screen failures or unacceptable sand production.

While drilling, consistent fluid treatment maintained the reversibility of FAZEPRO and an aggressive approach was taken to minimize acidinsoluble solids in the filter cake while drilling. The FAZEPRO fluid was diluted with premix to keep the acid- insoluble solids concentration below 5% vol./vol. When drilling was complete, the wellbore and riser were displaced with the FAZEPRO PST with WARP. The well was circulated and conditioned over 270 API and 325 API screens to remove any residual solids contaminants.

Prior to the expandable screens being run into the wellbore, fluid validation tests were carried out using the PST laboratory kit. The field requirement specified by the screen supplier called for three 750 mL samples per sample point is required to flow through the same 150- micron screen coupon. The benchmark for a fluid pass was that each sample had to show a trend with a consistent flow through time. Any deviation in the flow through time would have shown a propensity for screen plugging. Sample points were taken after one full circulation and two bottoms up during the reconditioning phase upstream of the shaker system. All fluid samples consistently passed the criteria set by the screen supplier. The success of this validation process allowed all screens to be run unimpeded into the wellbore.

Wellbore conditioning time was reduced greatly compared to conventional fluid operations. Generally, the FAZEPRO PST with WARP was circulated and validated over 1 ½ circulations. The other option would have been to screen up on the shakers while circulating the FAZEPRO RDF until all bridging agents greater than 40 microns was removed. This process could take days to accomplish compared to the time saved with the use of FAZEPRO PST with WARP. The fluid remained sufficiently clean throughout the running/expansion operations enabling it to be reused on subsequent wells.

After expanding the screen, a dedicated trip was made to spot the FAZE-OUT breaker system inside the screen. The FAZE-OUT breaker provided an average of six hours of delay to permit pulling out of the hole and closing the fluid loss control device, without losses.


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"Using FAZEPRO with WARP weighting agent permitted one injector well and five producer wells to be successfully completed with restrictive expandable screens. We set a record in one well."
Matt Thierens
Tech Service Engineer
M-I SWACO