ABSTRACT:

Discovered oil and gas fields after a certain production of oil and gas are regarded as mature fields. In these mature fields drilling infill wells, water-flooding and tertiary recovery methods may be used to increase production and recovery. The purpose of using one of these methods or their combination is to recover oil from the trapped or unswept zones in a reservoir. The objective of this study is to develop a numerical model to determine the best time to start infill drilling before irreversible pore collapse initiates and creates artificial traps and unswept zones. The developed model is derived by using the concept of body-centered pores in a cubic rock frame at microscopic level. On the basis of the derived model, a methodology named failure-curve method is proposed to determine the critical time of pore collapse. Thus, the best time for drilling infill wells is: before reservoir pressure/stresses touches the failure-curve. Sensitivity analysis technique is used to match the results of this study with experimental and field data, and it resulted in a good match. The model assumes that there are no constant thermal stresses and gravity forces. However, these forces might increase the creation of artificial traps and unswept zones in the reservoir.

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