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Oil provides 51% of Ecuador export earnings and a third of government revenue. Horizontal drilling has become an option to increase domestic oil production. The Yuralpa and Oso are land oil producer fields in Ecuador, which includes several wells. Some of the challenges include low pore pressure, sand control and the need of a filter cake breaker to enhance productivity. The reservoir drill-in fluid (RDF) and the breaker needed to be compatible, as well the operator required a breaker formulation that would not only allow the upper completion to be run before losing filtration control but also deliver superb productivity on completion after adequate soak time. It was also important that the solution as well required to be cost effective due to the low AFE that the operator had on the project. A water based breaker system, comprised of enzyme and chelant components, was chosen as the treatment selection. The thin RDF filtercake and the breaker treatment combination were tested in the laboratories to achieve an optimum technical and economical solution for the project. Due to environmental restrictions, sodium formate was used to provide density for drilling the horizontal hole section. After drilling, a mechanical and chemical wellbore clean up were performed, the pre-perforated liner was run, and the filter cake breaker was spotted at the open hole Potassium chloride brine was used as final completion fluid. Operations continue running in hole the upper completion assembly which some times includes an electric submersible pump (ESP). The usage of the novel breaker system allowed the project to achieve higher production rates than expected. Several wells have been successfully completed and put in production, all achieving or exceeding production expectations.
Oil provides 51% of Ecuador export earnings and a third of government revenue. Horizontal drilling has become an option to increase domestic oil production. The Yuralpa and Oso are land oil producer fields in Ecuador, which includes several wells. Some of the challenges include low pore pressure, sand control and the need of a filter cake breaker to enhance productivity. The reservoir drill-in fluid (RDF) and the breaker needed to be compatible, as well the operator required a breaker formulation that would not only allow the upper completion to be run before losing filtration control but also deliver superb productivity on completion after adequate soak time. It was also important that the solution as well required to be cost effective due to the low AFE that the operator had on the project. A water based breaker system, comprised of enzyme and chelant components, was chosen as the treatment selection. The thin RDF filtercake and the breaker treatment combination were tested in the laboratories to achieve an optimum technical and economical solution for the project. Due to environmental restrictions, sodium formate was used to provide density for drilling the horizontal hole section. After drilling, a mechanical and chemical wellbore clean up were performed, the pre-perforated liner was run, and the filter cake breaker was spotted at the open hole Potassium chloride brine was used as final completion fluid. Operations continue running in hole the upper completion assembly which some times includes an electric submersible pump (ESP). The usage of the novel breaker system allowed the project to achieve higher production rates than expected. Several wells have been successfully completed and put in production, all achieving or exceeding production expectations.
The Serrette and Savonette gas fields offshore Trinidad will be developed through use of open hole gravel pack (OHGP) completions. This completion type was chosen as the preferred completion technique for sand control for these fields. Due to a wide range of expected fluids densities required, the fluids design considered both monovalent and divalent brine as the base fluid for water-based reservoir drill-in fluid (RDF), completion brine and gravel pack carrier fluid (GPCF). Low pore pressures in the field did not allow applying high drawdowns during backflow of the wells, therefore chemical breaker technology was recommended by the Operator to be included in the fluids package to assist with filter cake removal and wells clean-up. The large pore throats of the formation necessitated the use of a high concentration of coarse sized particles in the RDF for bridging which caused a considerable decrease in retained permeability and potentially plugging of gravel and screen from assurance laboratory testing. High overbalances used during drilling potentially would exascerbate any near wellbore damage from the use of water based fluids.Most of the commercially available filter cake breakers are compatible only with monovalent brines and the acid precursors in use could not guarantee the low corrosion requirements required, nor result in ideal rheological properties expected from the GPCF over time since Hydroxy-ethyl-cellulose (HEC) was selected as the viscosifier to transport and deposit the gravel.GPCF with incorporated breaker, composed of a novel chelant compatible with divalent brines and a buffer, was chosen as a solution for the Serrette project. The system was modified for successful use on the Savonette Field. Screening tests were performed by the supplier to obtain an optimized formulation that would satisfy GPCF requirements and logistics. The final formulations were tested and approved at the operator's fluids laboratory. Several wells have been completed using the procedure and products. All have achieved outstanding production rates. The flow initiation pressures measured during wells start-up were noted to be less than those historically seen in the field.The GPCF with incorporated breaker is believed to have assisted with filter cake removal and well clean-up and also contributed to the fact that the gas requirements from the project have been met. The paper will focus on the development of fluids package for successful implementation in the field to deliver the wells and planned gas production.
This paper is about the study and utilization of Extra-Long lateral maximum reservoir contact (MRC) wells for development of the tightest and thinnest reservoirs in a giant offshore oil field in the Middle East. The objective is to derive production buildup towards company's target as economical optimized development plans are needed to maximize resource value. The key reservoirs for achieving the buildup target are characterized by poor quality rocks with permeability ranging from 3- to less than 1-md. Also, one reservoir is relatively very thin with 8 ft of payzone thickness where the oil resource density is low. Reservoir studies were conducted to overcome the challenges of developing these reservoirs that led to optimizing well spacing, orientation, horizontal lateral placement and maximizing lateral length to achieve objectives. For example, in tight reservoirs a 250 m well spacing was utilized for effective pressure support resulting in a high well density. MRC wells up to a maximum of 20,000 ft in lateral length are designed to maximize the productivity per well in low permeability formations while reducing the total well count resulting in reduced project capital expenditure (CAPEX) in terms of drilling and surface facilities costs by 20%. Extra-Long lateral wells also helped in reducing any potential anti-collision issues with current and future wells. The optimization of number and sequence of Extra-Long lateral MRC wells is expected to accelerate production build-up and minimize drilling costs taking into account the limited drilling rig availability. The development plans also accounted for implementing mitigations in addressing potential concerns encountered in the MRC wells life cycle from well construction process to production/injection phase. In the drilling and completion phase, new technologies were implemented for the first time and have resulted in a world record of completing the longest 6⅝in. cased lateral with a lateral length of 20,000 ft in one trip. These technologies have enabled accelerated delivery and lower construction costs for wells through application of a standardized well design process that helped in streamlining the drilling operations while reducing any potential risks. In the production and injection phase, all MRC wells are cased with 6⅝in. limited entry liners (LEL) to ensure full lateral accessibility for well intervention and retrofit operations. The specially designed liners ensure optimal stimulation along the lateral by providing mechanical diversion of the stimulation treatment delivered at high rate to provide more effective, cheaper and simpler stimulation operations. The utilization of sulphate reducing plant (SRP) for injection water with lower sulphate and particle content will reduce the number of stimulation and scale treatment jobs. Finally, all the preceding technologies and mitigations have led to successful implementation of the plan evidenced by production results that exceed production rate expectations from these challenging reservoirs.
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