Abstract
The main objective of this study is to improve the oil-based filtercake removal at the wellbore second interface through chemical method. The reductions in near-well permeability, bonding strength at wellbore second interface and acidizing treatment are the critical problems in oilfield upstream operations. One of the major causes has been identified as drilling fluid filtrate invasion during the drilling operations. This as result leads to near-well reduction in-flow capacity due to high drawdown pressure and wellbore instability. A number of chemical methods such as enzymes, acids, oxidizers, or their hybrids, have been used, however, due to the presence of a number of factors prior to its removal, there are still many challenges in cleaning oil-based filtercake from the wellbore surface. There is a need for development an effective method for improving oil-based filtercake removal. This study presents a novel Alkali-Surfactant (KV-MA) solution developed in the laboratory to optimize the filtercake removal of oil–gas wellbore. The Reynold number for KV-MA solution was found to be 9,068 indicating that turbulent flow regime will dominate in the annulus which enhances the cleaning efficiency. The wettability test established that, contact angle of 14° was a proper wetting agent. The calculated cleaning efficiency was 86.9%, indicating that it can effectively remove the oil-based filtercake. NaOH reacts with the polar components in the oil phase of the oil-based filtercake to produce ionized surface-active species; hence reducing the Interfacial Tension. Surfactant quickens the diffusion of ionized species from the interface to the bulk phase.
Highlights
The successful filtercake removal near the wellbore in horizontal oil–gas wells has been a critical issue in drilling and well completion operations as failure to effectively remove it would result to and reduction of permeability low as reported in various field cases (Leschi et al 2006; Ding et al 2006; Almond et al 1995)
Viscosity is observed to increase as the shear rate decreases again (Fig. 8)
As the shear rate affects the viscosity of the fluid, the shear rate can be used to predict the pumping pressure during the operations only at the shear rate at which it was measured (Caenn et al 2017)
Summary
The successful filtercake removal near the wellbore in horizontal oil–gas wells has been a critical issue in drilling and well completion operations as failure to effectively remove it would result to and reduction of permeability low as reported in various field cases (Leschi et al 2006; Ding et al 2006; Almond et al 1995). During acidizing treatment of formation to make the formation more productive, if oil-based contaminants enter the formation interval and are not removed therefrom the effectiveness of the acidizing treatment can be substantially reduced (Yuan et al 2002; Chan et al 1998). Due to the presence of a number of factors prior to its removal, there are still many challenges in cleaning oil-based filtercake from the wellbore surface. Oxidizing agents and acidic materials are very reactive, whereby they may lead to improper cleaning of filtercake residue, since minerals such as illites in sandstone reservoir are highly sensitive to acids. This would cause formation damage near the wellbore. Enzyme has a difficult time dissolving calcium carbonate particle (Al-Otaibi et al 2004a, b)
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