Clean-Up of Organic Wellbore Deposits Using Solvent Surfactant Combinations: Laboratory Development and Field Deployment

Abstract Well productivity often declines due to multiple reasons which include skin effect near well-bore area, heavy deposition in tubing, change in wettability etc. This paper presents a methodology to identify the optimal surfactant-solvent composition, followed by field deployment along with case studies of the laboratory designed formulation. The methodology is based on detailed characterization of crude oil followed by preparation of various surfactant-solvent combinations and evaluation of their efficacy in terms of improvement in rheological parameter, interfacial tension, contact angle and core flood experiment. The formulation was optimized based on the data of the above parameters. Core flooding experiments enabled validation and further optimization of the formulation based on observed differential pressure and permeability profile. In addition to cleaning the near well-bore area, designed surfactant-solvent combinations also aim to dissolve the organic deposit occurred around the fish stuck in the tubing. Three candidate wells (A, B, and C) were identified due to issues with poor inflow and sub-surface impairment. Wells A and B faced problems related to multiple fish stuck in the tubing, while Well C had poor inflow. Well A's crude oil was viscous with a tendency for wax deposition and therefore, waxy deposit surrounding the fish was identified as the probable reason for restriction of flow. A formulation containing Surfactant (1%), EGMBE (10%), LFI (1000 ppm), Xylene (40%), and HSD (48.9%) significantly improved rheology (99%) and IFT. However, experiments could not be conducted due to unavailability of crude oil from Well B. Well C’s crude oil, with a low pour point (12°C), responded best to a different formulation: Surfactant (1%), EGMBE (10%), Xylene (20%), LFI (2000 ppm), and HSD (69%). This combination reduced the viscosity, IFT and contact angle by 97%, 60% and 59% respectively. Field application of these formulations resulted in enhanced crude oil production up to 130%. The formulation also has the potential to dissolve the organic deposits surrounding the fish, pushing them toward the sump and thereby clearing the obstruction in the tubing.