A Novel Enzyme Breaker for Mudcake Removal in High Temperature Horizontal and Multi-lateral Wells

Abstract

Effective removal of drilling-mud filter cake during well completion is essential to reduce the formation damage caused by drilling activities in many production and injection wells. This task is very difficult to achieve, especially in horizontal/multilateral wells. Harsh chemical treatments (acids, oxidizers, and chelating agents) have been used extensively to conduct water-based mudcake cleanup treatments. However, these approaches have been limited due to the associated high corrosion rates and un-even mudcake removal. With their controlled reaction with the mudcake, mild chemical nature, better health, safety and environmental (HSE) profile, enzymes provide an excellent alternative to harsh chemical treatments in high temperature formations. However, their use has been limited to relatively low temperature applications due to their instability at elevated temperature values.In this work, two enzymatic systems were evaluated: old α-amylase system and new structurally reinforced α-Helix system. The old enzyme was found to form a potentially damaging precipitate at reservoir temperature above 100 o C. The degree of this damage was assessed using size-matching technique and core-flood experiments. This potential of secondary formation damage was drastically reduced in the new improved enzyme system. Enzyme denaturing was minimized by protecting the catalytic center using preferential hydration of proteins with a Polyol.The effectiveness of the new system was proven in the lab through comparative tests. Bioassay by reducing sugar estimation showed better biopolymer hydrolyzing capability of the new system at higher temperatures. In contrast to old enzyme system, core-flood experiments, conducted at high temperatures, using new enzyme system, showed the enzyme denaturing did not occur and the core oil permeability increased at stabilized pressure. In addition, this paper will also highlight the advantages and disadvantages of each enzyme system in terms of stability, compatibility, and mudcake damage reversal.

Development of Hybrid Drilling Fluid and Enzyme–Acid Precursor-Based Clean-Up Fluid for Wells Drilled with Calcium Carbonate-Based Drilling Fluids

“…These results are consistent with earlier results of Ghosh et al, 30 who reported that the clean-up efficiency of their investigated solution comprising 3% acetic acid and hydrolase enzyme was above 90%. Similar results are also reported by Al-Khaldi et al, 37 through coreflood studies.…”

“…This is consistent with the recommended limit of acid in the clean-up fluid as suggested by previous authors. 30 , 37 …”

“… 35 , 36 Enzyme solution (5 vol %) was prepared in 2 wt % KCl solution, and thermal stability was evaluated at 120 °C, using high-pressure/high temperature (HP/HT) cells, incubated for 4–12 h. This was followed by visual inspections at regular intervals for any physical change or coagulation following the method described elsewhere. 37 Slight cloudiness was observed after 8 h of thermal exposure; however, no coagulation was observed.…”

“…The detail can be found elsewhere . Current research has shown that with suitable modification of its macro-structure, α-amylase enzymes can achieve high temperature tolerance and maximum dissolution of the residual polymers (starch and xanthan) in the mud cake and thus disrupts the filter cake for the acid to attack uniformly. , The hydrolysis of a biopolymer by this enzyme system progresses sequentially, leading to synergistic complex formation with the substrate and rendering it suitable for hydrolysis. , Enzyme solution (5 vol %) was prepared in 2 wt % KCl solution, and thermal stability was evaluated at 120 °C, using high-pressure/high temperature (HP/HT) cells, incubated for 4–12 h. This was followed by visual inspections at regular intervals for any physical change or coagulation following the method described elsewhere . Slight cloudiness was observed after 8 h of thermal exposure; however, no coagulation was observed.…”

Insights on Potential Formation Damage Mechanisms Associated with the Use of Gel Breakers in Hydraulic Fracturing

“…They catalyze the hydrolysis reaction of the β-1,4 glycosidic bond between the mannose molecules in the polysaccharide backbone to produce simple sugars such as monosaccharides or disaccharides that are soluble in water. Some examples of enzymes used in the oilfield include Amylase, Cellulase, Hemicellulase, Pectinase, and Mannanase [ 57 ].…”