The under balanced drilling technology has been under applied to the oil and gas well since the first cable tool well drilling. By the advent of rotary system the drilling fluid modified into mud system for controlled and smooth drilling operations. The under balanced technology revived again in mid-70’s due to the fore most need of such technology that can enable monitoring of reservoir fluid influx while drilling in progress and minimize reservoir damage. Some of the major prospect of under balanced drilling includes depleted zones, sub-normal zones and naturally fractured reservoirs. Where the prevailing myth about UBD Technology is its utilization in naturally fractured reservoirs, this paper will help to unfold enhance reservoir production achieved by UBD technology in conventional reservoirs.
The purpose of this paper is to acknowledge the UBD Technology in conventional reservoirs, specifically. The prospects of application will be discussed with a major focus on mature reservoirs (reduced formation damage in depleted formations) and newly developed fields. Early Screening for the right reservoir and different screening criteria for the application of UBD technology in conventional reservoirs will help the readers to understand the limitations and applicability. The economic and technological advantages will be discussed along with value added by UBD technology in the form of increase reservoir production in normal pressure reservoirs which mostly get damaged to some extent with conventional drilling techniques.
The paper will briefly describe the scope of UBD in Lower Indus and Middle Indus Basin. Through the work that has been done in similar reservoirs in Middle East, analogies will be developed. For further understanding, feasibility criteria of projects in local context will be considered that will enable the operators to take decision accordingly. The paper will also briefly explain the application of under balanced technology in normal pressure reservoirs with its limitations depending upon the UBD equipment safe pressure ratings in relation to reservoir pressures.