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Block M is an extra-heavy oil Reservoir located in the Orinoco Belt in Venezuela. It has been exploited via cold production utilizing east-west orientated horizontal wells in cluster with well spacing of 600 m or 300 m, which caused an uneven reserve utilization and unfavorable oil recovery rate. This situation motivated the study of optimal well placement strategies to obtain higher reserve utilization degree, higher primary recovery, and more attractive economic benefits during the period of contract. A full field-scale dynamic simulation model was created and history match was performed, to quantitatively analyze the distribution of cold-production exploitable remaining oil and remaining potential. Based on the understandings, strategies were proposed for future well deployment, including infill well. And then, a technically and economically favorable full-field development scheme was recommended based on economic evaluation. The study showed that the remaining oil distribution in developed area is mainly controlled by well pattern, oil-gas gravity separation, reservoir heterogeneity, and etc. The inter-well area in the developed area with 600 m well spacing, especially for the lower units of production interval, shows a relatively high cold production remaining potential; and so does the area directly beneath the platform due to horizontal well displacement configuration. For undeveloped areas, east-west orientated well spacing was recommended to reduce to 200–250 m; for developed areas, east-west orientated infilling wells were suggested to be drilled preferentially in the lower unit, under the condition that inter existing-well formation pressure remains above 65% of the initial pressure. Besides, at most three wells per pad were proposed to be drilled in a south-north orientation to drain reserves directly beneath an adjacent well pad. The recommended development scheme would recover 8% of OOIP during the contract period. Several north-south orientated wells had been implemented, and presented favorable production performance, with an average initial production rate of 1.5 times of neighboring existing east-west orientated wells. Compared with the generally adopted horizontal well placement scheme in the Orinoco belt, that is, in east-west orientation and with large well spacing, the study innovatively proposed a novel one, which can provide a guideline for exploitation of similar reservoirs in the Belt. |
