A Thorough Diagnostics-Solution Approach to Increase the Recovery Factor from Horizontal Wells in Complex Dolomites

Abstract

Xan is Guatemala's largest oil field, accounting for more than 90% of the country's production. Xan produces from a complex dolomite reservoir at average rates of 10,500 BOPD, with most of the production coming from 8 horizontal wells with typical open-hole completion lengths of 1,500 ft. The majority of the horizontal wells at Xan do not produce at their fullest potential because of near wellbore damage, associated to drilling fluid residues, and problems related to the high production of water, averaging 90% water cut at the field level. This paper presents an innovative approach combining diagnostics supported with fiber optics distributed temperature survey data feedback and matrix stimulation systems, tailored to address specific needs, including viscous-highly retarded emulsified acid systems, multifunctional solvents, and surfactant visco-elastic diverting agents, all deployed through coiled tubing to remove the damage and maximize the treatment penetration in the reservoir. The solution was tested in two horizontal wells with severe formation damage and water production problems. The use of coiled-tubing deployed fiber optics facilitated monitoring and evaluating the stimulation treatments and fluids behavior in realtime, by capturing a sequence of temperature profiles and temperature responses to the acid injection at different times through the treatment. As a result, zonal coverage and effectiveness of the stimulation and diversion systems could be quantified as the treatment was pumped; allowing optimization of the stimulation program and pumping variables to accommodate to the actual well's response. Production results have been outstanding, oil production increased by 54% from the two horizontal wells, which is equivalent to the production of a brand-new development well in this field, at a much lower cost. The diagnostics-solution approach developed for this reservoir helped accurately diagnosing the problem and implementing a fit-for-purpose stimulation treatment that actually improved oil production. The proposed methodology has substantially changed the process of stimulating horizontal sections in the Peten basin of Guatemala.