The fields in southeastern Mexico have produced from Cretaceous and Jurassic-age naturally-fractured carbonate reservoirs since the early 1970s. Many recent exploratory wells drilled and completed in these high-pressure, high-temperature formations have yielded unsatisfactory results due to a combination of causes, including severe drilling-induced formation damage to low-matrix permeability reservoirs. Conventional completion and stimulation treatments to remove and bypass the damage have yielded satisfactory results in some cases but not in others. To increase productivity from new discoveries, an integrated approach to the completion and stimulation of low-permeability naturally-fractured carbonate reservoirs is proposed.An innovative technique, combining dynamic under-balanced perforating with a highly-stable emulsified acid and a nondamaging viscoelastic surfactant-based acid, is presented in this paper. Three successful applications in southeastern Mexico are documented, including a low-productivity development well; a well originally perforated and stimulated using conventional technology; and an exploratory well, resulting in substantial production increases in all three cases. These applications served to prove that the combined effect of the proposed completion and stimulation technologies was the enabler to achieve superior production results. The highly-retarded emulsified acid pumped through clean perforating tunnels produces longer fracture penetrations, positively impacting the performance of low-permeability reservoirs and resulting in improved production responses. At the same time, the viscoelastic system reduces leakoff, which is necessary to extend fracture lengths further in the reservoir. The fluids combined in a high-rate pumping technique that consisted of alternating stages of emulsified acid, main acid, and diverter reduced the creation of wormholes near the wellbore, thus increasing the penetration of the treatment in the reservoir.

With the discovery of new fields becoming less common and the need to maximize economic recovery in mature fields, operators are trending towards rig-less intervention work to reduce cost and delays to production related to traditional workover rig interventions. With its field complexities, from low bottom hole pressure (BHP) to high temperature/high pressure (HT/HP) reservoirs, and from consolidated sandstone to naturally highly fractured carbonates, and large producing intervals in various flow units with active aquifers, southern Mexico poses a highly significant challenge for rig-less intervention in water control and zonal isolation to assure placement and accuracy of treatment fluids. This paper discusses the implementations and results of two case histories in which a cost-effective application involving coiled tubing and inflatable packer systems were used for water control in a high water cut producing well and for well abandonment of a newly completed well. The utilization of coiled tubing combined with the inflatable packer is able to precisely deliver the treatment fluids to the zone of interest while the production tubing remains in place, which enhances timely and cost effective intervention solutions1 when compared to workover rig operations. Case 1 presents the water control application using a coiled tubing inflatable packer system in combination with an organic crosslinked polymer gel, and micro-fine cement slurry for a naturally fractured carbonate reservoir in southern Mexico. The result of this innovative rig-less approach exceeded the operator's expectations. The case history well was producing 815 BOPD and 5.2 MMSCFD with a water cut of 77%. After the water control treatment with the coiled tubing inflatable packer system, organic crosslinked polymer gel and micro-fine cement slurry, the well was producing 1,459 BOPD and 5.15 MMSCFD with a water cut of 0%. Case 2 demonstrates a newly completed well with production tubing and packer already set and the well producing with high water cut from an open-hole completion. By using the inflatable packer system through coiled tubing and squeezing cement slurry to abandon the open-hole, a new interval could be perforated and exploited in just 28 hours; in contrast, conventional abandonment with a rig can take up to 10 days.