Abstract

This work investigates the combined use of horizontal wells and hydraulic fracturing technology to improve steam utilization and process efficiency on steamflood operations. Enhancement of the production response obtained when combining both technologies was modeled using a fully implicit 3-D thermal reservoir simulator. The advantages of using hydraulic fracturing for thermal processes and especially for steam injection operations are explained by the "Heat Plane Source" concept presented here. Different scenarios for fractured horizontal wells were modeled: orthogonal, longitudinal, horizontal and multiple fractures.

During conventional steam injection operations, heat convection and gravity effects become dominant in the near-wellbore region resulting in excessive heat losses and a heat chest of limited extent. Simulation results indicate that inclusion of hydraulic fractures will ensue better steam utilization and sweep efficiency improvement while minimizing convective oil override and reduction of operational costs.

The cost effectiveness of the combined approach was evaluated using a decision analysis process and incorporating the production response into an economic model. Profitability was evaluated based on the Net Present Value response. Results suggest an accelerated and marked increase in cash flow, particularly during the early life of the project.

The application of fracturing technology for steamflood operations will accelerate the response and overall performance from heavy crude reservoirs. The discussed approach is applicable to thinner reservoirs, dipping reservoirs, steam distillation drives and especially effective in layered reservoirs.

Approach

The main objective of this work is to investigate the performance of hydraulically fractured horizontal wells and their advantageous application for thermal recovery processes. Reservoir simulation was used to evaluate the combined use of horizontal wells and hydraulic fracturing as production techniques for improved steam management, effective field development, accelerate recovery, development of depleted zones, target bypassed oil banks, assisted gravity drainage scenarios and alternative completion/recompletion approaches. Analysis based on the productivity increase and ultimate cumulative recoveries indicate that the proposed approach may be an attractive production strategy for more efficient thermal recovery processes in heavy and intermediate oil reservoirs.

Thermal Recovery Processes

In-situ combustion, cyclic steam stimulation (Huff-n-Puff), continuous steam injection and hot water flooding are the basic thermal recovery processes. Thermal methods rely on several displacement mechanisms to recover oil. The relative importance of each mechanism depends on the type of oil being displaced and the related recovery process. Mechanisms such as; distillation drives and thermal expansion of the heated oil will add to recovery as crude distillation tends to reduce residual oil saturation. Lighter oil fractions vaporizes providing a miscible flood front in advance of the thermal front. However, thermal processes rely on crude viscosity reduction due to temperature increases as the most important recovery mechanism.

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