Effective High-Density Wellbore Cleaning Fluids: Brine-Based and Solids-Free

Abstract

Displacing drilling mud with clear solids-free completion brine is a critical step during well completion. As we move into deeper waters and drill to deeper depths (greater than 25,000 feet MD), conventional methods and cleaning fluids become a limiting factor in this phase of the operation. Conventional cleaning fluids use fresh water or seawater treated with surfactants to remove wellbore solids and water-wet tubulars. Using low-density cleaning fluids creates a negative differential pressure between the working kill weight fluid and the formation, casing, and cement liners. In many situations, the negative differential pressure cannot be tolerated, and the risk of failure at the liner top, etc., is increasedespecially, if the wellbore has not been pressure-integrity tested. Additionally, with increasing rig/spread costs, high pump rates are necessary to decrease the time it takes to perform these operations. The pump rate is indirectly proportional to the pump pressures required. Weighted spacers decrease the overall pressure differential, which allows for higher pumping rates.To overcome the density limitation of these cleaning fluids, conventional techniques, such as additional hydraulic horsepower, backpressure schedules, the addition of solids to lighter cleaning fluids (e.g., water, seawater), or balancing the weight of the low-density cleaning fluid with a matching higher-density fluid is used. However, each of these "fixes" has inherent limitations and is accompanied with reduced cleanup efficiency. Furthermore, conventional surfactants are not active or effective in high-density brines. New brine-compatible surfactant chemistry and the corresponding balanced-displacement engineering design were developed to overcome limitation of conventional displacement technology.This paper describes the field applications of new brine-based, high-density, solids-free cleaning fluids in balanced-displacements in deepwater and offshore shelf wells. The new high-density fluids were based on new surfactant technology developed to ensure effective wellbore cleaning, wellbore design parameters, and displacement modeling. In addition, weighted spacers aid in reducing high pump pressures and wellbore pressure differentials. In one case history, a maximum pumping pressure of more than 9,000 psi was expected for conventional water-based displacement but was reduced to a little more than 3,000 psi with the new design. Highdensity cleaning fluids, with densities up to and greater than 17.5 ppg, have been formulated and used successfully without compromising cleanup efficiency and significantly reducing differential pressures. Results from laboratory development and field applications are presented.

Application of High-Density Brines in Drilling and Completion Fluids: Current Insights and Future Perspectives

“…Turbidity is a measure of the extent to which water’s transparency is diminished as a result of the existence of particles that are suspended inside it. Turbidity in brines, which are characterized by high salt concentrations, can arise from the existence of suspended solids, including clay, sand, or other particulate substances . The turbidity level in a brine solution can be quantified by employing a turbidity meter, which gauges the extent of light diffraction or absorption caused by particles suspended within the solution.…”

“…Turbidity in brines, which are characterized by high salt concentrations, can arise from the existence of suspended solids, including clay, sand, or other particulate substances. 93 The turbidity level in a brine solution can be quantified by employing a turbidity meter, which gauges the extent of light diffraction or absorption caused by particles suspended within the solution. The findings are commonly presented in Nephelometric Turbidity Units (NTU), a widely accepted metric for quantifying turbidity.…”

Nanoemulsion Applications in Enhanced Oil Recovery and Wellbore Cleaning: An Overview

“…Nanoemulsion has the biggest impact on the EOR mechanism by which it can aid to recover the residual oil from the reservoir rock. The droplet size of the nanoemulsions that are smaller than the pore throats in gravel packs and in reservoir matrix rock resulting good infectivity and penetration without filtration and they are not issue to gravity-driven separation due to the density differences of the two phases [34]. It represents the development and application of materials, methods, and devices, in which critical length scale is on the order of 1-100 nm.…”

“…Displacing drilling mud with clear solids-free completion brine is a critical step during well completion. As we move into deeper waters and drill to deeper depths, conventional methods and cleaning fluids become a limiting factor in this phase of operation [34].…”

Development, Testing, and Field Application of a Heavy-Oil Pipeline-Cleaning Chemical: A Cradle-to-Grave Case History

“…A review of generic oil degreaser and solid-removal technology yielded fi ve key parameters important to effi cient chemical cleaning (Buzelin and de Campos Lima 2008;Javora et al 2008;Bordalo and Oliveira 2007). These parameters collectively enable the hydrocarbon and inorganic scale to stabilize in the water or chemical phase.…”