Abstract

A new technology utilizing a Single Step Specific Enzyme Breaker (SSSEB) process has been applied to horizontal wells for the removal of filter cake caused by drill-in fluid (DIF). This technique has resulted in significant improvements in well performance. Previous SEB (Specific Enzyme Breaker) technology, published by O'Driscoll et al (1998) and Beall et al (1996), focused primarily on a two step process for removal of DIF filter cake damage; an initial SEB treatment for starch or xanthan polymer removal followed by a second treatment of acid for calcium carbonate removal. This new SSSEB method provides an effective "one step" system for removing both the starch polymer and calcium carbonate components of DIF filter cake.

Case history information and laboratory data are presented to validate the effectiveness of the SSSEB formulation on the degradation of the filter cake formed when a starch, xanthan and calcium carbonate DIF is utilized. Previous laboratory and field data have demonstrated the effectiveness of SEB technology for degrading starch polymer. The new SSSEB method utilizes the identical starch specific enzyme product used in previous SEB treatments; however, it also employs a buffered, organic acid fluid. The organic acid reacts with the calcium carbonate portion of the filter cake as the enzyme simultaneously acts on the starch polymer. Compared to conventional high strength mineral acid systems, the SSSEB acid solution reduces the risk of fluid emulsions, formation acid sensitivity issues, secondary precipitate problems as well as safety and environmental issues. The new system is also relatively slow-reacting, allowing for uniform filter cake deterioration.

The most noticeable economic benefit resulting from the application of the SSSEB system is increased production of hydrocarbons. The single step technique also offers savings on rig and related charges, chemical costs and operational charges by allowing for wells to be placed on production more rapidly and not requiring follow up acid work.