Swelling Elastomers Improve Well and Reservoir Management in Horizontal Wells

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This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 107882, "Improved Well and Reservoir Management in Horizontal Wells Using Swelling Elastomers," by Majid Abdullah Mahrooqi, SPE, Ghaliba Hinai, and Franz Marketz, SPE, Petroleum Development Oman, prepared for the 2007 SPE Annual Technical Conference and Exhibition, Anaheim, Califoronia, 11–14 November. The paper has not been peer reviewed. To increase recovery from maturing reservoirs, Petroleum Development Oman (PDO) is developing the capability to detect and shut off unwanted water and gas. Swelling elastomers (SEs) have been deployed to segment horizontal wells in combination with surveillance and shut-off technologies. In beam-pump wells, dual wellheads have enabled logging while pumping. Introduction The South-field fields in southern Oman mostly are mature oil fields operated by PDO. The fields produce medium-gravity viscous crude with viscosity ranging from 200 to 550 cp. The fields have been producing since the mid-1980s. Initial field development was by vertical wells. Since the mid-1990s, development has been primarily with horizontal wells. Production is from a combination of eolian and glacial sediments. Reservoir heterogeneity is high. Almost all South field wells must have sand control. The horizontal reservoir section is appproximately 350 to 500 m long and may cross both reservoirs. The horizontal section is drilled with a 6 1/8-in. drill bit and completed with a standalone 4 1/2-in. sand-control liner using 200-μm wire-wrap screens (WWSs) in open hole. This results in an open annulus between the sand-control liner and the formation. More than 90% of the wells are artificially lifted by use of beam pumps, hindering accessibility because of surface units and rods. Since the start of infill drilling, the new oil production has been dominated historically by high initial water levels, and as of 2002, new wells produced an average of 3 bbl of water for every 1 bbl of oil during their first year of production. SEs SEs have been available for a number of years, and recently the oil industry has become more interested in them. Some SEs are water based and some are oil based. Because of the high water production from startup in the South field, water-based SEs were selected. The theory is that specially designed rubber elements will swell, when contacting formation water, to seal off the annulus between the completion and the wellbore. A key element to achieve improved oil recovery through well and reservoir management in a horizontal well is segmenting the well into different flow units. SEs are being deployed to enable segmentation. The SE tool provides zonal isolation through the swelling of the elastomers when contacting produced water in the wellbore. Fig. 1 shows a casing joint with SE seals.