Published: 01/01/2010
Published: 01/01/2010
An operator in the Caspian region needed to optimize stimulation for horizontal OH wells. The operator had been using chemical diverting systems with no significant improvement to the production profile after the treatment. Looking for a solution that would offer diversion and fluid loss control during the acid fracturing procedure, the operator contacted Schlumberger.
Schlumberger engineers proposed an acid treatment with two main fluid systems—MaxCO3 Acid system and SXE emulsified acid. The SXE acid is a viscous, highly retarded, concentrated acid system formed with a 70:30 hydrochloric acid-to-oil ratio, stabilized with an emulsifier. Because it can penetrate farther into the formation than any live acid, SXE emulsion was used for deep penetration. The MaxCO3 Acid system achieves superior diversion through degradable diversion technology. The combination of these two fluid technologies creates a system that improves leakoff control on naturally fractured reservoirs as compared to conventional acid-alternate gel systems used in acid fracturing.
A staged sequence followed. After a prewash of 15% hydrochloric acid (HCl) to break down the formation and push hydrogen sulfide (H2S) out of the wellbore, the first MaxCO3 Acid system stage was pumped. Bracketed by 15% HCl, the main 28% SXE acid followed. This procedure was repeated twice more to increase the etched half-length of the fracture and to increase the coverage of SXE acid through the entire open hole. The best results were achieved when the MaxCO3 Acid system stage was pumped at below fracture pressures to get the best plugging efficiency. The MaxCO3 Acid system and SXE acid disintegrated following the treatment, leading to excellent cleanup and zero formation damage.
An overall production gain of 1,010 m3/d was almost twice the return of 517 m3/d that the client expected. This production gain was achieved from three wells—similar to that obtained from six wells in the operator’s previous stimulation campaign in the same field.
An overall production gain of 1,010 m3/d, which was achieved from three wells, is similar to that obtained from six wells in the operator’s previous stimulation campaign in the same field.
Challenge: Provide diversion technique to achieve effective stimulation throughout a naturally fractured horizontal openhole carbonate well.
Solution: Applied MaxCO3 Acid degradable diversion acid system and SXE emulsified acid to divert and create multiple fractures in the openhole lateral and control fluid loss.
Results: Achieved production increase of 1,010 m3/d - nearly twice the operator’s anticipated gain.
