Downhole Deployment Valve Adds Opportunities to the Oil and Gas Industry
Authors: Grayson Brian 
Published: October 2008

Abstract
As the Oil and Gas Industry becomes more aware of the extent and detrimental effect of formation damage in wells drilled conventionally, the underbalanced drilling and completionof wells is becoming more widely used and accepted. Along with limitations to formation damage, underbalanced operations offer additional benefits such as improved penetration rates, increased production potential and production while drilling. As with many new technologies, along with the advantages they offer come certain drawbacks that need to be addressed such as added cost and safety concerns. Chief among these is the issue of safety while tripping pipe into or out of the hole and the installation of complex completion bottom hole assemblies.
Since in traditional underbalanced operations the well is allowed to flow, a flowing or shut-in pressure is always present in the annulus requiring that specila precautions be taken during tripping operations to control it. Several well to minimize the pressure or using a snubbing unit. All of these methods carry certain disadvantages and limitations. The Downhole Deployment Valve (DDV) has been developed to overcome the barriers and simplify the common procedures associated with underbalanced operations.
This paper will present the concept of a Downhole Deployment Valve (DDV), and detail how its design and operation enhance the safety and efficiency of the underbalanced program while alleviating the cost and time required to trip pipe and bottom hole assemblies. This paper will further support the concept with details of a field application and how it has benefited this operation.

Introduction
Increased awareness of the degree of formation damage caused by fluid invasion into the reservoir during conventional overbalanced drilling techniques has resulted in a growing interest in the benefits offered by Underbalanced Drilling (UBD). These techniques, though not necessarily suitable for all reservoirs, can have a considerable position impact in such instances as :Depleted reservoirs where in-fill wells can be drilled with little of no damage.Highly permeable and fractured reservoirs where fluid invasion can be greatly limited and consequent degradation of permeability reduced or eliminated.Hard formations where greatly increased penetration rates can be achieved. However, along with the many benefits offered by UBD techniques come some disadvantages, such as higher associated costs and increased perceived risk and safety issues. Perhaps the most significant risk is during the normal process of tripping the drill string to change the bottomhole assembly (BHA). Since the formation is allowed to flow during UBD operations, a surface pressure is ever present in the annulus, which is controlled by a rotating control head. Once tripping begins and the pipe is being stripped through the well head, this pressure must be handled in some manner before a "pipe light" situation is reached.
Killing the well one current method used to control the well, and allows for the drill string to be tripped into or out of the well conventionally.