As development of hydrocarbon reserves continues to move into deeper and more complex reservoir conditions, operators have found that conventional techniques for testing, perforating, and stimulating have not been capable of providing satisfactory results in the severe well conditions. Even if operationally satisfactory, they have been unable to meet the goals for cost efficiency.
This paper describes an experience in the Tropical Field, located in eastern Venezuela and operated by Repsol - YPF in which the reservoir is characterized by high-pressure reservoirs and complex geology due to faults and high-dip-angle formations. Repsol needed a method that would optimize well testing operations, improve safety, and cut costs without compromising the results of the operation; thus, a major change to traditional drill stem testing operations was needed. A technique, which would eliminate the need to kill the well to retrieve the guns and also provide the flexibility to test, evaluate, and fracture the well, was suggested. Instead of using a drilling rig or a work-over unit as in the standard drill- stem testing operation, the procedure would allow the operator to perform a rigless well test evaluation using optimum underbalanced conditions in favor of the reservoir.
Several alternatives were evaluated for perforating and testing the well. After thorough examination of all possibilities, snubbing- and coiled-tubing-conveyed perforating (CTCP) methods were selected as the most promising alternatives for achieving the objectives proposed at the beginning of the project. While coiled tubing had been used to perforate in other areas in Venezuela, coiled tubing combined with snubbing had not been used in Venezuela.
This paper will focus on the methods developed to satisfy the operational challenges, the results obtained with the use of the newly applied technologies, and how the technology was able to address the operator's needs as well as the difficult reservoir conditions. Instrumental in the success of the methodology was the combined use of super-deep penetration technology, state-of-the-art memory tools for depth correlation, real time data transmission, and the flexibility to perform several operations during a rigless well-test evaluation. This case history represents the first live-well intervention using snubbing and coiled-tubing perforating techniques performed successfully in eastern Venezuela.