Single Step Enzyme Treatment Enhances Production Capacity on Horizontal Wells

Abstract A new technology utilizing a Single Step Specific Enzyme Breaker (SSSEB) process has been applied for the removal of damage caused by drill-in fluid on horizontal wells. This technique has resulted in significant improvements in well performance. Previous SEB (Specific Enzyme Breaker) technology, as it applies to xanthan, starch and carbonate drill-in fluid, focused primarily on a two step process for removal of horizontal well drill-in fluid filter cake damage; an initial SEB treatment for starch or xanthan polymer removal followed by a second treatment of acid for calcium carbonate removal.1,2 This new SSSEB method provides an effective one step system for removing both the starch polymer and calcium carbonate components of drill-in mud filter cake formed during horizontal open hole operations. 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 drill-in fluid 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 (such as hydrochloric acid) often used for calcium carbonate filter cake removal, 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 system is also relatively slow-reacting which is important for the effective placement of the breaker fluid across the entire horizontal interval and allows for uniform filter cake deterioration. The most noticeable economic benefit resulting from the application of the Single Step Specific Enzyme Breaker system is increased production of hydrocarbons. The SSSEB 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.