Novel Application of Modified Enzymatic Fluid System for Freeing Stuck Pipe in Gas Wells

Abstract While Enzymatic treatment is considered safe for downhole tools and an effective technique for the removal of biopolymer-based drilling mud cake formed during drilling, a novel application of enzymatic system has been developed and successfully utilized to release stuck pipe while drilling. An enzyme's function is intrinsically linked to its three-dimensional structure, defining how it achieves substrate binding, catalysis, and regulation. Stuck pipe contingency especially in horizontal/multilateral wells demands large volumes of harsh chemicals like acid, solvents, and other chemicals potentially damaging to the reservoir and downhole tools. This paper aims to demonstrate the function of a robust all-enzyme system that can break down the biopolymer mud cake responsible for stuck pipes at harsh downhole conditions. Freeing stuck pipe jobs executed in cooperation with one of the largest National Oil Company in Asia in an exploratory well drilled located in the North-Eastern fields. The 8 ½″ hole was drilled deep with logging-while drilling tool. Later the logging-while drilling tool was assembled with a rotatory BHA assembly and lowered for pipe conveyed logging. While lowering this tool at around 10000 ft, stuck was observed and multiple unsuccessful attempts for freeing string were carried out. A mud-acid job was carried out followed by HSD spotting and string shots, without any apparent success. Given the severity of the problem joint operation teams including the product designer, decided on the pilot application of this advanced Recombinant Enzyme H system. A pre-flush solution was pumped before pumping the enzymatic solution at the stuck region. After allowing a minimum soaking time the working on the string was carried out. The drill pipe was freed within 5 hours of enzymatic solution soaking after a loss of about 9 rig days. The drill collar severing job plan was canceled, and expensive logging tools were successfully retrieved. Drilling continued in the same section as planned. The enzyme application dissolved the friction causing cake acting around the stuck region and reduced surface area of contact to release all the differential stuck. This was a novel approach by the Operator showcasing the potential of this technology in freeing stuck pipes quickly and economically.