Water control is one of the greatest challenges in Southern Mexico wells, where the reservoirs are generally fractured carbonates. Many of the wells have early water breakthrough as a result of one or more of the following: water coning, near- wellbore flow, high-conductivity channels, high-conductivity layer breakthrough, segregated layering, and inadequate completions. In cases where it is possible to shut off the producing interval and recomplete the well in a new interval, reticulated polymer gels and/or cement slurries can control water production. However, when the water is produced in a different interval than the oil, the success rate of reducing the water cut is less than 30%. In these cases, waterless cement slurry squeezes have proven to be an effective solution to unwanted water production. This method has been used to successfully reduce water cut in several fields in South Mexico with a nearly 100% success rate. A well which was carefully evaluated as a candidate and then treated with a waterless cement slurry resulted in a reduction in water cut from 71% to 5%, while oil production increased from 290 barrels of oil per day (BOPD) to 1054 BOPD. In addition, the deferred production was greatly reduced using this technique—less than four days compared with several weeks using alternative techniques. Water cement squeezes are a cost-effective way to reduce water production in the producing intervals of naturally fractured reservoirs. This technique has increased oil production while resulting in significant cost savings in terms of both treatment costs and deferred production.

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With the discovery of new fields becoming less common and the continued development of brownfields, water control is becoming increasingly essential to enhancing oil recovery. Water control operations are especially challenging in under-pressured reservoirs with openhole completions, such as in the Boscan field in West Venezuela. Gravel-packed slotted liners and standalone premium screens are common completion methods in this field. Dual injection, combined with permanent water shutoff (WSO) gels or relative permeability modifiers to control water production in these completions has traditionally produced inconsistent results. This method can fail to change the well production profile and possibly damage oil-producing layers. This paper will discuss the development, implementation, and results of an innovative solution for water shutoff that was engineered for the complex completion methods mentioned. The solution involves three key stages; the temporary isolation of the producing layers, the permanent shutoff of the water zones, and the effective cleanup of the isolated producing layers. The results of ten water control treatments are presented here. The average water cut was reduced to 30% from 88% and oil production was increased by an average of 300 BOPD per well through the application of this water shut-off solution. In one particular well, two previous water control treatments using a conventional water shutoff technique, including a relative permeability modifier (RPM), had left the well producing 100% water. The new solution reduced the water cut to 25%, resulting in a gain in oil production of 300 BOPD. This innovative solution was established as a standard practice for water shutoff in the Boscan field. Introduction The Boscan field lies 40-km southwest of Maracaibo, Venezuela and covers an area of approximately 660 km2, produces a 10.5°API gravity asphaltic oil from the upper Eocene, Boscan (Misoa) Formation with a live oil viscosity ranging from 200–400 cp at reservoir conditions. The reservoir dips to the southwest and ranges from 5000 to 9000 ft in depth. Boscan Field is a combination structural/stratigraphic trap. The reservoir sands were deposited in a tidal-dominated depositional setting. Boscan Field has a complex stratigraphic framework, the interpretation of which is made particularly difficult by the 1 to 0.6 kilometer well spacing. The field currently produces ~ 115,000 BOPD. Figure 1 shows the geographic location of the Boscan field. Since its discovery by the Richmond Exploration Company in 1947, the Boscan field has had over 800 wells drilled with 525 of them currently active. Most of the shut-in wells in the field are located in the south end of the field that in recent years has experienced a surge in water production. Most of the wells in this particular area are experiencing water cut of 90% or higher. Problem Scope The main production challenges in south Boscan wells are;Surface facility limitations in handling produced water; therefore the volume of fluid produced is limited. In addition, production enhancement is restricted.

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.

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.