Direct emulsion water-based drilling mud system helps operator overcome challenges
In the Delaware Basin of New Mexico, shallower formations, such as the Salado, include halite and anhydrite layers followed by weaker formations in the Delaware Sands- (e.g., the Brushy Canyon). The fracture gradient difference between these two zones has typically required an intermediate casing string to seal off salt formations before reducing fluid density to drill ahead into the Delaware Sands and deeper shale sequences. Achieving an effective three-string well design with one cased intermediate section requires significant fluid density management to help prevent lost circulation, which is impacted by the dissolution of salt into the mud system.
A range of drilling fluids has been used in previous wells having three-string casing designs in the Permian Basin. Over time, unsaturated salt fluids invaribly wash out the halite, leading to increased mud weight (MW) and hole enlargement, which requires an increased cement volume. As a result of rigorous laboratory experimentation, careful planning, and successful execution, a direct emulsion water-based drilling mud (DEWBM) was applied in the field to address these challenges. The DEWBM system maintained salt saturation, as evidenced by the return of salt cuttings to surface, and reached fluid densities as low as 9 lbm/gal. Emulsifying oil in saturated sodium-chloride brine enabled this DEWBM to advance as a potential fit-for-purpose solution.
The results obtained while drilling with the DEWBM system in trial wells are compared with those from offset wells drilled using other fluids. Early indications show heightened efficiency and reduced total well costs.
Click below to view further details and download the technical paper (PDF).
Source: 2018 AADE Fluids Technical Conference and Exhibition, 10-11 April, 2018, Houston Texas, USA
Authors: Rusty Connell (Occidental Oil and Gas) | Derek Adam (Occidental Oil and Gas) | Linsay Earle (Occidental Oil and Gas) | Occidental Oil and Gas | JJ Miller (Halliburton) | Justin Langley (Halliburton)