The water shut off technique is applied in some wells as a remediation plan to restore their production after an early water breakthrough from U reservoir in the Iro field of the Oriente Basin, Ecuador. The production historical data, workovers and sandbodies correlation are compared among wells to understand the reservoir behavior, the shale baffle sealing continuity, the existence of different sand units and the impact on their production. Few years of heavy oil production with abrupt water increase conducted to squeeze perforations in the lower part of pay zones. Production behavior before and after water shut off is analyzed regarding water cut, formation water salinity, fluid provenance from the reservoir and its zone perforations setting during completions. The stratigraphic well correlation, reservoir properties and sealing shale layers explain the well production outcomes and geological patterns. Well intervention lessons learned and recent pulse neutron logs support additional water shut off proposals at current Iro producer wells. The U sandstone reservoir development was focused on the Lower U sequence while hydrocarbon potential was identified in Upper U sequence. Nevertheless, the geoscientist kept the main interest in Lower U reservoir development because of their oil in place volume. The strong water drive aquifer caused mostly a fast water cut increase achieving 90% in around three months and well’s production continued for few years until economical cut. In order to keep wells in active status, squeeze jobs were planned and executed, dropping the water cut to less than 10% followed by a gradual ramp up during many years of production. The fluid rates were reduced drastically from average 10000 bfpd to less than 1500 bfpd. The formation water salinity increased from 18000 ppm to 60000 ppm. These evidences advice of two different production behavior in the Lower U sandstone reservoir. The re-perforations were done above a shale layer seal which separates sandstone units. This seal is controlling the water breakthrough in many wells. However, there is evidence of sandstone units connection to the western area of the field, because of salinity decrease and pressure increase. After many years of production, pulse neutron logging was run showing flushed zone from former producing perforations as well as remaining hydrocarbons at thin sandstone layers deposited in the upper unit of Lower U sandstone reservoir. In addition, this document will allow reservoir engineers to forecast production behavior, to plan water shut off in analog fields, accordingly.

This paper summarizes the strategies implemented in a mature oil field in Ecuador to revive its production by improving energy efficiency, increasing fluid production and incorporating proved reserves. Results are shown in terms of the field energy efficiency index, energy consumption on ESPs, oil production, annual production decrease tendency and reserves incorporation. The Choke Model philosophy was implemented as a strategy for field development optimization. This methodology allowed the operator to identify that the main chokes were the production wells and the power. By using divergent and convergent thinking techniques focused on these chokes, four main strategies were selected: reduce the pipe diameter size of a fluid line, artificial lift system energy assessment, reactivate closed wells and recomplete others. Complete description of the methodology is provided in detail to permit readers to analyze this successful case. The reduction of pipe size diameter of a fluid line increased the mobility of the fluid from the well pads to the plant, eliminated the recirculation of water and thus increase the energy efficiency indicator of fluid handling from 9,770 to 10,190 BFPD/HP. The energy assessment of the artificial lift systems identified the inefficient wells that were scheduled for ESP redesign and technology upgrade with an energy improvement of 30%. All these energy efficiency improvements lead to rise fluid production. Based on the possibility to increase fluid production, wells reactivations, ESP upsizing’s and recompletions were planned. The team used a screening process to optimize candidates, gaining 2,010 BOPD, in average, over the baseline production profile since September 2017 to December 2018. The activities performed and well interventions diminished the annual oil production decline rate from 14% to 8%, allowed the operator to incorporate 4.8 MBBLS of proved reserves in 2018 and generate 7.6 MUSD of free cash flow in the same year. All the strategies were successfully achieved, and they accomplished the objectives of reviving a mature field, extending its life and generating value for the operator. None of the previous were possible without rethinking energy sustainability and reservoir management. The novelty of this work is the multidisciplinary approach and innovation methodology implemented to provide solutions to operational field chokes by identifying feasible projects in terms of technique, time and economics.

The high water cut 98,5% caused the abandonment of a directional well, which was reactivated after 3 years using a water shut off technique. Offset wells production behavior, stratigraphic seal layers distribution, reservoir properties, and cased hole logging data played a relevant role for the well planning, reactivation and production success of heavy oil from the mature Amo field in the Oriente Basin of Ecuador. The Lower U reservoir production screening from neighbor wells and stratigraphical well correlation supported a rigless acquisition plan of pulse neutron logs to diagnose the fluid flow patterns after 5 years of production and 3 years of a well abandonment. Further corrosion and cement log was run to check the well integrity and compared it with initial cement log to discard possible cement channeling suspicion behind casing. Finally, water shut off well program was carried out. The acquired neutron logs showed flushed zone from two former producing perforations as well as remaining hydrocarbons in the upper perforated zone. The gamma ray log activation was detected just below the oil water contact while the oxygen activation log "OAI" was highlighted just above the gamma ray activation at the same depth where CBL log experienced picks perturbations suggesting bad cement an possible channeling behind casing. The OAI ended just in the upper unit perforations where another CBL pick was recorded. These evidences supported possible cross flow hypothesis from the bottom to the top producing zones. The water shut off job squeezed the lower perforation zone and re-perforated the upper unit to reactivate the abandoned well. The cement and corrosion logs suggested a good conditions of casing and zone isolation from aquifer. The well reactivation produced 700 bbl/d of water formation (100% BSW) during a month, the water salinity gradually increased from 16000 ppm to 45000 ppm NaCl. Likewise water cut diminished to 17% and 170 bbl of oil was pumped daily after voiding the cross flowed fluid (44000 bbl). Furthemore, the unknown productivity index for ESP pump design was unveiled. Stratigraphic well correlation indicated the shale layer continuity and thickness variability, which in combination with shale buffers occurrence were controlling the production behavior in offset wells. These aspects led to get updated cased hole logging data to identify opportunities for re-activation of abandoned well unlocking by-passed oil reserves after successful water shut off job execution.

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