Single-Stage Chemical Treatment for Oil-Based Mudcake Cleanup: Field Case and Laboratory Studies

Abstract

Formation damage minimization and removal are important factors in enhancing field productivity and achieving targeted production rate. While formation damage is anticipated during drilling, an effective wellbore cleanup fluid becomes essential to remove mud damage and enhance well productivity. Filter cake layer created by drilling fluid can impair production considerably and should be removed prior to production using an effective treatment. Filter cake can be removed using a chemically designed filter cake removal treatment. The design of the treatment requires considerations of mud type and reservoir conditions. Also, it is important to consider the compatibility aspect of the treatment fluid with formation fluids and drill-in fluid base oil. Incompatible fluids result in precipitation which leads to further formation damage. In Saudi Arabia, many sandstone reservoirs are drilled with invert emulsion drill-in fluid to avoid the risk of clays swelling, which can lead to hole sloughing and formation damage. However, production impairment due to mud damage effect was observed in some horizontal wells drilled with invert emulsion drill-in fluid and completed with stand-alone screens as a result of improper mud managemet. After being put on production, their production rates have been reduced significantly with time. The decrease in production was related to screen blockage and mud cake impairment. A newly developed single-stage treatment was spotted and soaked to remove oil based mud cake and screen blockage. A significant sustained improvement in production was noticed and flowback solids indicated removal of screen blockage and mud cake. Lab studies were conducted at reservoir simulated conditions to evaluate the effectiveness of the treatment. The study covered testing the treatment filter cake removal efficiency, return permeability tests with reservoir core samples, and compatibility tests with formation fluids and drill-in fluid base oil. This paper will discuss in detail the laboratory work conducted and the successful field treatment performed.

Evaluation of Nonreactive Aqueous Spacer Fluids for Oil-based Mud Displacement in Open Hole Horizontal Wells

“…With the advent of microemulsion technology, nonreactive aqueous treatment fluids can be customized to achieve a relatively more effective well cleanup. Microemulsions are thermodynamically stabilized multicomponent fluids composed of oil, water and surfactant blends, which solubilize the oil component of the OBM with limited mechanical agitation [16][17][18][19][20][21][22] . Since acid-free microemulsion fluids are incapable of dissolving OBM solid particles, it is critical that dispersed residual filter cake solids are able to flow through the sand screen completion apertures when used in standalone screen completions.…”

A novel alkali-surfactant for optimization of filtercake removal in oil–gas well

“…Furthermore, the presence of such filtercake prevents the formation of strong bonds between cement and rock, resulting in weak points where failure can occur (Lichinga et al 2020). The most important practice during oil-gas well drilling and completion designs for optimizing oilfield development is the effective cleanup of oil-based filtercake from the wellbore (Al-Otaibi et al 2010).…”

Novel Cake Washer for Removing Oil-Based Calcium Carbonate Filter Cake in Horizontal Wells

“…Leschi et al and Al-Kuait et al proposed the use of organic acid precursor (OAP) and water wetting additives [40,41]. Micro-emulsion solutions formulated from alcohol and surfactants have been suggested [42][43][44]. Another approach utilizing an oxidant agent (persulfate salt) and a non-ionic surfactant has also shown some improvement in filter cake removal [45].…”