Schlumberger

Performance Report: IFE Service was a Natural Fit for International Project in Bohai Bay

Challenge: This international operator required a high-performance oil-base mud for drilling the upper section, a non-damaging inhibitive reservoir drill-in fluid (RDF) for the production interval, and the ability to properly dispose of all cuttings on the rig site. Analysis of the producing formation indicated the formation contained a D90 pore opening size of 250 microns and lab tests have indicated that the filter-cake breaker treatment is most effective if the filter cake is composed of at least 66% acid-soluble material. This required the operator to use coarse calcium carbonate bridging agent in a “sacrificial” mode and the utilization of shale shakers with fine screens to remove cuttings while drilling the production interval. This process puts a strain on the CRI unit as it is necessary to dispose of a large amount of calcium carbonate in addition to drill solids.

Solution: Having a significant amount of used FAZEPRO and VERSACLEAN fluid in storage, the operator realized substantial savings from converting this used FAZEPRO and used VERSACLEAN fluid into recycled VERSACLEAN fluid to successfully drill the 12¼-in. upper hole section. As multiple sands with interbedded shale stringers were targeted, an inhibitive RDF was required. Extensive lab testing by both M-I SWACO and the operator indicated that FLOPRO NT fluid with KLA-STOP inhibitor would be the ideal RDF to drill the 8½-in. production interval. OPTIBRIDGE software was used to determine the optimum blend of calcium carbonate in the FLOPRO NT system. The optimum blend included 20 lb/bbl (57 kg/m3) Carb 40 and 25 lb/bbl (71 kg/m3) Carb 250 additive. To ensure effectiveness of the filter-cake clean-up treatment a high quality filter cake was required. This meant a minimum RDF specification of >50 lb/bbl (143 kg/m3) calcium carbonate and <20 lb/bbl acid-in-solubles (AIS) in the system. M-I SWACO developed a field test for determining both specifications. The M-I SWACO ES group used a customized CRI unit on the rig to grind down, slurrify and inject all solids (cuttings and calcium carbonate) from both intervals.

Result: While drilling the 12¼-in. upper-hole interval, no hole problems were encountered and the rate of penetration (ROP) was significantly higher than with any previously used water-base system. While drilling the 2,799-ft (853-m) production interval, approximately 90 MT of calcium carbonate were added to the FLOPRO NT system. There were no hole problems (e.g., backreaming, packoffs, washouts, slow ROP) encountered while drilling the 8½-in. interval. Below is the fluid specification chart that was generated by the M-I SWACO field engineers on location. It tracks: fluid density, concentration of calcium carbonate, AIS and MBT. All IFE objectives and benchmarks were met and the client saved approximately $128,350 by efficiently deploying three of the M-I SWACO product lines. The cost savings were attributed to recycling FAZEPRO and used VERSACLEAN fluids.


Download: INTEGRATED FLUIDS ENGINEERING (IFE) Service was a Natural Fit for International Project in Bohai Bay (0.54 MB PDF)

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“All benchmarks and objectives were met by combining the efficiency of VERSACLEAN fluid for drilling the upper section, the inhibitive and non-damaging characteristics of the FLOPRO NT system for the production interval, and a cuttings re-injection (CRI) process for handling the cuttings.”
Mark Dick
Bohai Bay Project Manager
M-I SWACO