Schlumberger

Performance Report: FAZEPRO RDF Turns Problematic Offshore Wells into Producers without Screen Failure

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.

Well Information
Location Bohai Bay, China
Interval drilled 300 to 1,200 m, 25 to 35% porosity unconsolidated sandstone
Borehole temperature 120 to 150ºF (49 to 65ºC)
Produced oil 16 to 22 API gravity
Oil viscosity 10 to 80 cP
Completion type Openhole, standalone screen
Screen type 150‐ or 230‐micron woven mesh screen
Formation pore opening size 50 to 300 microns

Close monitoring of maximum/minimum limits of AIS and calcium carbonate along with fluid density occurred while drilling the wells (Table 1). This type of monitoring results in placement of a filter cake composed of predominately acid‐soluble material. Coarse calcium carbonate (approximately 1.5 metric tons) was added to the FAZEPRO system during drilling. As is typical, 200‐mesh screens were run on the primary shakers to maximize the accumulation of AIS material.

Once the completion assembly was in position, the following displacement sequence was implemented: base oil, viscosified spacer, buffered completion fluid w/emulsion preventer (pH 3.5–4.0), viscosified spacer, buffered completion fluid w/emulsion preventer (pH 3.5–4.0), completion fluid w/emulsion preventer, completion brine, 15% acetic/5% HCl acid soak.


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“By utilizing reversible technology, such as FAZEPRO and FAZEPRO SF fluids, the major operator has drilled and completed over 15 wells in Bohai Bay, China without any screen failures or unacceptable sand production.”
Mark Dick
Bohai Bay Project Manager
M‐I SWACO