Many current deepwater and high rate wells are being completed in an openhole environment as openhole completions provide the greatest opportunity to maximize reservoir flow potential. Current technology, however, lacks the subsurface control necessary to effectively manage the reservoir in situations where sand control is required. ExxonMobil is pioneering technologies to model well performance more accurately and to provide subsurface control during completion and production operations. The first hardware developments within this initiative build on the success of Alternate Path® and NAFPacSM gravel packing technologies and address water or gas breakthrough in openhole, multi-zone gravel pack completions. ExxonMobil affiliates collaborated with third party suppliers to design and qualify new hardware to facilitate zonal isolation, extend gravel pack reach, and simplify rig site operations. This process included engineering design, component testing, and full-scale prototype evaluation. First application of this technology is targeted for early 2008.
This paper discusses newly developed sand control screen hardware that is enabling technology to perform openhole gravel packs with true zonal isolation. The equipment provides the ability to seal off bottom water, selectively complete or gravel pack targeted intervals, perform a stacked openhole completion, or isolate a gas/water-bearing sand following production. Application of the technology is expected to extend well life and ultimately increase volumes and reserves capture.
Background
Continued economic success in remote or deepwater environments requires delivery of high rate, high capacity, and long-life wells. In these developments, it is often necessary to drill and complete high angle wells, penetrating multiple pay intervals and incorporate sand control technologies. Reservoir conditions, wellbore geometry, and production performance expectations can all introduce significant cost and complexity that frequently limit application of traditional cased hole sand control techniques. Openhole gravel pack completions are now commonly installed to connect multiple payzones over long intervals and improve well productivity.
Because openhole completions have no perforation tunnels, formation fluids can converge on the wellbore radially from 360 degrees, thus eliminating the additional pressure drop associated with converging flow and then linear flow through gravel filled perforation tunnels. The reduced pressure drop, associated with an openhole sand control completion, virtually guarantees that it will be more productive than an unstimulated, cased hole gravel pack in the same formation. Operationally, openhole techniques eliminate the need for costly cementing, perforating, and clean-up operations, the complexity of stacked completions, and in some areas an additional casing string or liner. The downside, however, is that openhole completions do not have the same level of installation flexibility and subsurface control to manage geologic and reservoir uncertainty versus traditional cased hole gravel pack techniques. Operators are particularly challenged in their ability to manage fluid inflow along the wellbore in openhole completions, including avoidance of watered-out or depleted zones during installation and shutting off unwanted water and gas during production.
