Abstract

Economic recovery of shelf reserves in Gulf of Mexico asset has been made more efficient by using a rig-less, through-tubing (RTT) completion equipment package. The package integrates all services and personnel needed for the completion and charges on a day rate-plus-material basis. The RTT approach has been used to repair wells that have developed sand-control issues and still have justifiable reserves to recover. The techniques can be used in abandonment of depleted zones and completing untapped zones.

The equipment package is modular and adaptable to each well's needs, and all personnel concerned have experience in multiple disciplines. The added benefit is a single, simplified invoice; compared to multiple invoices as is the case when using discrete services. The equipment packaging and day rate-plus-materials (DPM) pricing structure allows for a more accurate estimation of cost and reduces unplanned variable costs. There is a lower delivery cost using dual-purpose equipment and multiple-discipline personnel, which has the added benefit of optimizing manpower and equipment needs while decreasing exposure to hazards. Based on the economic drivers of the project, new technology can be implemented, further improving either time savings, increasing reserve recovery, or both. All of the above factors allow for real-time cost-tracking, enabling decision-making based on the current status of the project.

The primary focus of the paper is on remedial completions and workovers to install an economically viable form of sand control for the latter-day producing life of the wells. Case histories demonstrate how the application of this approach has proved to be the preferred method and a viable means to repair sand-control problems for producing zones, complete new zones, and abandon depleted zones for many wells in the Gulf of Mexico Shelf.

Introduction

Over the past 10 years there has been an increased emphasis, in Gulf of Mexico operations, on recovery of smaller-asset reserve packages. The rig-less, through-tubing (RTT), vent-screen system has become a viable method that is both flexible and cost-effective. The RTT vent-screen method is a crucial element in the efficient production from mature-asset reservoirs.

Vent-screen completion methods have been used in many wells in the GOM. Development of important technologies associated with vent-screen applications has presented the opportunity to deploy a novel completion process that reduces completion costs, improves completion efficiency, extends the life of the completion, reduces mechanical risks, and improves the rate at which the reserves can be recovered.

The packaging of the equipment package designed exclusively for wellbore preparation, deployment of vent-screen or other sand control methods, and placement of sand control proppant or sand pack along with multidisciplined personnel to man the equipment, has added further to cost-effective RTT completion approach. Also the modification of existing equipment, such as wireline double-drum units, to double-drum combo wire- and electric- line units has made it possible to get all the necessary equipment required for RTT into the confined spaces of platforms and mid-sized jack-up boats.

New pricing structures of day-rate-plus-materials (DPM) have the added benefit of simplifying cost estimation and unplanned variable cost. Spread rates can easily be calculated by multiplying project length times day rate and adding material cost. This calculation can speed the decision-making process on the risk vs. return of potential reserves. All contribute to a more streamlined and efficient process for getting hydrocarbons through the sales meter.

Fig. 1 shows the support equipment necessary to blend, mix, and pump the fluids and solids used in a sand control application. Fig. 2 shows a double-drum combo unit.

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