Unique Methodology for Well Re-entries Requiring Sand Control Improves Production Potential

Abstract

In re-entry or workover type situations, the primary performance objectives determined during the initial well completion remain the same, especially in deepwater, high-rate wells. These generally require running the largest-diameter casing string possible, since the dimensions of the completion equipment can determine critical well objectives. Especially in reservoirs requiring sand-control reliability, production rate becomes a primary concern in the workover situation. Issues regarding critical erosional velocities, reservoir sweep or recovery efficiency and feasibility of installing flow controls or intelligent-well equipment remain. For mature wells requiring a side-track, the current well-construction practices necessitate reduced dimensions of the sand-control completion-equipment. This paper presents a well construction/completion methodology that supports increased completion-component dimensions in side-tracked or new wells, potentially improving overall well performance. The system is suitable for any openhole gravel-pack completion. Introduction Because of the prevailing high prices of hydrocarbons and the difficulty in finding new reserves, the oil and gas industry has made efforts to increase the rates of recovery in mature fields. The average rate of recovery is 35% for oil and 70% for gas; however, the current direction is to try to increase the recovery rate of oil to 50% and more than 80% for gas.1 Mature fields — also called brown fields1 — are those oil and/or gas fields that are approaching the end of their productive life. Typically, these mature fields have been producing for more than 30 years and are located in certain geographical areas for different historical and geopolitical reasons. Brownfields are commonly located in the North Sea, United States (onshore), South America, Russia and Australia. These fields produce over 70% of the world's oil and gas production. Brownfields possess the advantage of an existing infrastructure, providing the least expensive means to increase reserves and production. In both enhanced reserves recovery projects for mature fields using sidetracks from existing wellbores and for new well field development projects, wellbore size and casing design requirements are key determinants for well construction costs. Yet, wellbore size and tubulars designs must be balanced against cost factors in order to accommodate certain critical requirements, including:rig- and drilling-equipment limitationssub-sea preventer stack dimensionsexisting wellbore geometry and trajectory limitations for sidetrackstubular sizing needed for reservoir productivityhole size needed to accommodate gravel-pack completionscasing size needed for downhole flow-control equipmentcasing size needed for artificial-lift equipment. Oil fields developed for openhole deviated or openhole lateral gravel packs typically install and cement production casing or liners. The openhole production interval is then drilled using the next smaller bit size. The single-trip method described in this paper is more cost efficient in that it does not require changing hole sizes and eliminates at least one pipe round trip. In this new method, the production liner and hanger are combined with the openhole gravel pack assembly and run into the well in a single trip. The gravel-pack service tool and accessory equipment is configured to allow gravel packing and liner cementing in consecutive operations within the same pipe trip. In this paper, a system, which targets an economical increase in production and reserves in mature unconsolidated reservoirs/fields, is described. The methodology accomplishes these achievements through using:Larger screen ODs, which improve flow area and screen life, thereby increasing productionMinimized pipe trips, which impact completion costs by saving rig time and wearA one-shot deployment of liner and screen with an option of gravel packing and liner cementation.