This case history paper presents the first multistage fracture stimulation of a mature field well in Ecuador using a hydraulic workover unit deploying jointed pipe. The process used a hydrajet perforating application followed by tubing-path pumping of the fracturing treatments. To place fractures properly in each pay zone, effective diversion is required. This has been a challenge in many fields of Ecuador. Furthermore, multistage fracturing completions have represented a complex process when applying conventional methods because of the number of operations involved, such as perforating, fracturing, setting isolation plugs, and cleaning out the wellbore for each interval. Several trips into the well are often required, which adds time and costs to the entire completion intervention. Because of the absence of some information as well as the presence of upper open perforated intervals, the hydrajet assisted fracturing (HJAF) process, which uses highly effective abrasive jet perforating immediately before the fracturing stage, was used to provide a degree of flexibility for making additional decisions and performing changes during the operation. This paper presents the detailed workover planning, multiple customized fracturing designs, operations data, and the stimulation results of the case study. The multistage hydraulic fracturing technique was designed and applied to individually fracture stimulate three formation layers in the Ecuador mature field. The method allowed using customized treatments for each zone and more aggressive fracturing schedules to promote high fracture conductivity or length when necessary. Successful production from the mature Ecuadorian field was achieved using the multistage hydraulic fracturing HJAF method. Additionally, this method does not require mechanical zonal isolation between stages. The HJAF technique provides an attractive option for applications in similar wells to help recover additional reserves.

Low-energy and compartmentalized reservoirs make flowback more difficult than in conventional reservoirs following massive fracturing treatments. Conventional guar-based fracturing fluid systems can cause additional skin damage to the fracture because of fluid residues. Low-residue polysaccharide-based fracturing fluid systems, compared to conventional systems, provide a smaller residue percentage according to laboratory tests, and this result agrees with flowback data from wells discussed in this paper. Costs in primary treatments associated with operational events, such as flowback time, can be considerable for well completion operations. Guar-based fracturing fluid systems were used at the beginning of this basin study. After analyzing flowback and early production data, it was decided to change to a low-residue polysaccharide-based fracturing fluid system and to maintain other variables constant, such as injection rate, proppant concentrations, and treatment schedules, to compare fluid performances, cost benefits, and post-stimulation production rates.This paper summarizes results for 70ϩ fracture stages in 30 wells, with an average of 150,000 gal of clean volume per stage and 250,000 lbm of proppant. Guar-based fluid fracturing systems comprise 25% of this study with an average flowback time of 231 hours with 30% (at most) fluid recovery. On the contrary, 75% of the treatments used a low-residue polysaccharide-based system, which required an average of 110 hours of flowback time, while only 10% of the volume was recovered to deliver to production facilities because of the lack of water percentage.Metal-crosslinked low-residue polysaccharide-based fluids are more sensitive to shear stress than borate-crosslinked conventional systems, and they can become unstable at high injection rates and reduced pipe diameters (3 1/2-in. tubing). Increasing tubing friction requires more hydraulic power to apply the same amount of net pressure at the fracture. According to the diameter restriction, this study includes pumping through pipes with diameters larger than 5 1/2-in., therefore making sensitivity to shear stress a nonissue.Low residue polysaccharide-based fracturing systems represent an early production alternative for massive fracturing treatments because of their low residue percentage. These fracturing systems can be

PEMEXАвторское право 2015 г., Общество инженеров нефтегазовой промышленности Этот доклад был подготовлен для презентации на Российской нефтегазовой технической конференции SPE, 26 -28 октября, 2015, Москва, Россия.Данный доклад был выбран для проведения презентации Программным комитетом SPE по результатам экспертизы информации, содержащейся в представленном авторами реферате. Экспертиза содержания доклада Обществом инженеров нефтегазовой промышленности не выполнялась, и внесение исправлений и изменений является обязанностью авторов. Материал в том виде, в котором он представлен, не обязательно отражает точку зрения SPE, его должностных лиц или участников. Электронное копирование, распространение или хранение любой части данного доклада без предварительного письменного согласия SPE запрещается. Разрешение на воспроизведение в печатном виде распространяется только на реферат объемом не более 300 слов; при этом копировать иллюстрации не разрешается. Реферат должен содержать явно выраженную ссылку на авторское право SPE.