An Assessment of an Uncomplicated Drill-in Fluid and Its Application to a Wide Range of Global Completions and Their Recent Successes

Abstract

An established non-biopolymer reservoir drill-in (NBRDF) system which was developed in very early 2000 for high-density drilling applications – approximately 11.5 to 17.5 lbm/gal – was recently improved to provide functionality in low-density drilling applications – as low as 9.5 lbm/gal. Global implementation of this system over the last several years has demonstrated not only flexibility with respect to drilling and completing in diverse reservoirs but also its application as a workover system. In addition, this system was recently optimized by incorporating compatible chemistry to mitigate atypical damage mechanisms. As such, several case histories are presented to demonstrate the system's broad functionality with respect to density, completion type, reservoir, and logistics, as well as its capacity to reduce near-wellbore/formation damage. This non-biopolymer reservoir drill-in fluid (NBRDF) system demonstrates relatively high tolerance to solids and reservoir fluids as well as ease of hydration when mixing on the rig. Routinely the hydraulics are consistent and predictable even as no biopolymer is utilized. This system is compatible with the incorporation of an inhibitor, specifically, a scale inhibitor to mitigate calcium carbonate and minor sulfate scaling. This system recently incorporated a sized calcinated magnesium compound (MC2) and sized magnesium complex (MC3) which promotes viscosity, specifically low-shear rate viscosity, at a lower density range that was not achievable before. The initial concepts of buoyancy of solids and the exclusion of a biopolymer as incorporated in relatively high-density brines formed the basis for the development of this system. These concepts are discussed first to provide a background for the preceding recent improvements and case histories. Each case history presents a different set of objectives whereby pre-planning assessments were implemented to address and mitigate perceived risks as related to the fluids. The methods employed include assessments for rheology, scaling, hydraulics, displacements, compatibility and formation damage. The drilling and completion results for these projects exhibit a wide range of applications as well as flexibility with respect to required density, completion hardware and reservoir type. The procedures utilized for each project are evaluated with respect to specific drilling and completion targets and include the iterations/modifications required; subsequently the field learnings are also discussed.

New shale hydration inhibitors adapted to the downhole conditions

“…The other important application of polyol compounds in drilling fluids is related to their ability to adsorb on metal surface. These chemical compounds have the ability to reduce the coefficient of friction on the metal-metal and metal-rock contact (Akram et al, 2016;Aziz et al, 2016;Luyster et al, 2016;Jasiński, 2017;Sayindla et al, 2017;Xiao et al, 2017;Zhao et al, 2017;Zhu et al, 2017;Kania et al, 2018). Propylene oxide polymers have the ability to reduce the coefficient of friction, the most effective was polypropylene glycol with the lowest molecular mass of 200 u.…”

Drilling muds with stable rheological parameters using modified natural polymers

“…The improvement of gel strength and the possibility of reducing the concentration of natural polymer in the drilling mud (cost reduction) can be obtained by applying modifications with the use of appropriate metal ions. The possibility of reducing the polymer concentration in the drilling mud in this case is a result of significant increase in viscosity due to the molecular weight increase (Kramer et al, 1987;Harris, 1993;Himes et al, 1994;Queiroz and Santos, 2000;Lomba, 2002;Suresh Kumar et al, 2012;Dupas et al, 2013;Luyster et al, 2016;Zhu et al, 2017).…”