Formation Damage Control Utilizing Composite-Bridge-Plug Technology for Monobore, Multizone Stimulation Operations
- Garry Garfield (Baker Oil Tools)
- Document ID
- Society of Petroleum Engineers
- SPE Permian Basin Oil and Gas Recovery Conference, 15-17 May, Midland, Texas
- Publication Date
- Document Type
- Conference Paper
- 2001. Society of Petroleum Engineers
- 2.2.2 Perforating, 1.10 Drilling Equipment, 1.8 Formation Damage, 4.1.2 Separation and Treating, 3 Production and Well Operations, 1.14 Casing and Cementing, 1.6 Drilling Operations
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Composite bridge plugs (CBPs) save operator time and money by enabling quick and easy installation and removal. CBPs can be installed under pressure in multi-zone, commingled gas wells without using expensive formation kill weight fluids. Kill weight fluids can reduce production from the well, and in some cases have damaged newly fractured zones to the extent that production has been cut in half.
After remedial operations, CBPs can be removed using coiled-tubing-conveyed milling equipment in one fourth of the time required to mill traditional cast iron bridge plugs. Formation damage can be substantially reduced using low viscosity milling fluids that easily remove composite cuttings from the wellbore. This is especially important because of the low annular velocities characteristic of coiled tubing operations. The wellbore is left cleaner than those using cast iron bridge plugs in similar operations.
CBPs can withstand high pressures for up to 10 days without compromising their pressure integrity and without the need for a cement barrier on top of the CBP. Initial field runs have demonstrated that the CBPs can be milled as quickly as 30 minutes compared to 2 hours for milling conventional cast iron bridge plugs. Multi-zone, commingled gas wells using as many as 7 CBPs have been brought back on production after taking only 12 hours to remove all CBPs, including rig-up and rig-down of the coiled tubing unit. Field runs also indicate CBPs can be milled quickly when set at depths exceeding 19,000 feet.
Formation damage as a result of installing and removing traditional cased hole plugging devices has been dramatically reduced due to the development of composite bridge plug technology. The CBP was developed primarily to give the operator the option of setting several cased-hole bridge plugs in a single wellbore to isolate multiple zones. The operator can quickly remove them from the wellbore using conventional milling tools after the remedial operation has been completed. Composite bridge plugs enable the operator to independently treat and test several zones, selectively isolate each zone, and then remove multiple bridge plugs in an under-balanced environment. Typically, the under-balanced removal of composite bridge plugs is accomplished with coiled-tubing-deployed downhole motors and milling tools.
An operator's main objectives in completing a monobore, multizone gas well are to independently perforate, treat, and isolate each zone of interest without damaging the formation, and to leave a clean wellbore that will produce the zones when the treatment of each zone is complete.
Cast iron bridge plugs and retrievable-type bridge plugs have been used in the past to isolate multiple zones in a wellbore for selective treatments. Cast iron bridge plugs require heavy-weight fluids to remove cuttings from the wellbore. These heavyweight fluids have the potential to damage lower pressure zones. In a well with multiple zones, using multiple cast iron plugs in a single wellbore can make removal of the plugs very difficult due to the heavy weight of the cast iron cuttings under the mill and the difficulty in circulating the cast iron cuttings from the wellbore. When using multiple retrievable-type bridge plugs, the operation of setting and retrieving the plugs can amount to twice as many runs in the hole as with CBPs. Even considering the speed of wireline methods for retrievable bridge plugs, removing multiple CBPs by coiled tubingis still more cost effective.
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