Design of a Cyclic Steam Stimulation Pilot Test for the Orinoco Oil Belt. A New Vision About Steam Injection Flow Rates

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Abstract In some of the giant extra-heavy oil fields from the Orinoco Oil Belt (OOB), the challenge is to increase recovery over primary production by about 10%, to meet its ambitious development plan. To get this, it is necessary to apply EOR processes. It is visualized the integral design of a cyclic steam stimulation (CSS) pilot test, using a high steam injection rate. It is identified and quantified the main variables and operational parameters affecting the performance of CSS, for an oil field at OOB. The design of this pilot test covers the location of the area, visualization of thermal well, identification and quantification of the variables that potentially influence to a greater extent the performance of this technology, conceptual design of EOR surface facilities and a complete monitoring plan. A cluster with 10 long horizontal wells of different lengths is evaluated. The variables studied are: specific steam flowrate per unit length of well, well length, and well thermal insulation. We apply design of experiments to select the combinations of the values taken for the different variables. The duration of the different stages in every cycle is given by previous results applying optimization of CSS to sector modeling. The main constrains dictated for the thermal well are identified and taken into account to define the maximum steam injection and production rates for this test. The pilot test is simulated for three complete cycles, with two approaches: High (2.2 – 3 bbl/day*ft) and Low (1.5 bbl/day*ft) specific steam flowrates. Important production variables as drawdown, bottom-hole pressure, field average pressure, gas oil ratio and water cut have been evaluated. Results for the main operating parameters (High/Low approaches), and the economic evaluation, are shown. These results show once again that higher specific steam flow rates get higher recovery and are even more profitable. The study encourages a review of the paradigm that limits steam injection rates in high-productivity projects currently underway at OOB. Additionally, it is identified that at present is the thermal well and not the surface facilities, which limit the application of CSS at higher rates, needing an urgent improvement in its concept. The steam injection rate is conventionally expressed as daily rates (bbl/day), absolute amounts per unit thickness of formation (bbl/ft), etc. This practice creates misunderstandings, especially in the case of horizontal wells. The variable proposed in this study (specific steam flow rate per unit length of well) is valid for any type of well, and it has a physical significance related to well injectivity. Another novelty introduced in this study is a higher specific steam flow rate (2.2-3 bbl/day*ft), between 50% and 100% higher than references found in the literature (1.5-2 bbl/day*ft).