Engineering the Mud-Spacer-Cement Rheological Hierarchy Improves Wellbore Integrity

Abstract

Maintaining the density hierarchy for wellbore fluids has been a routine while achieving a proper rheological hierarchy for mud, spacer and cement could have been compromised due to tedious testing and sometimes limitations in the field. Establishing appropriate rheological and friction pressure hierarchy prevent fluids (mud-spacer-cement slurry) intermixing especially in deviated and horizontal wells. The objective of this paper is to present a spacer rheological properties model along with a new micro-emulsion spacer formulation which improves well integrity. This water-based spacer system, with densities ranging from 8.5 to 16 ppg, was modeled to temperatures up to 325°F and provided proper suspension properties, confirming stability at bottomhole circulating elevated temperatures. In addition, ccompatibility of this spacer package with various synthetic based muds, oil based muds and cement slurries, designed for Gulf of Mexico, the US land, North Sea and the Middle East, plays a significant role in achieving great displacement efficiency, wellbore clean up, long term effective zonal isolation and sustainable hydrocarbon production. It is not always possible to accomplish the turbulent flow. Therefore, a rheological model was developed to accomplish the ideal viscosity hierarchy by optimizing the spacer formulation design. Optimum rheological hierarchy occurs where the viscosity profile of a spacer system is higher than the viscosity profile of drilling fluid and lower than the cement slurry. Model's predictions have been validated by one atmospheric and two industry-known HPHT rheometers. The model predictions show that the rheological profiles of the spacer fluid, for all the main standard shear rates, are between the mud and cement profiles. Data obtained from field case histories show the improvements and added values such as ideal fluid compatibility, better displacement efficiency, friction pressure hierarchy and effective zonal isolation,

Application of Microemulsion Systems in the Formulation of Biodegradable Pre-Flush Fluid for Primary Cementing

“…Therefore, by analyzing the studied systems, it is possible to observe that there was a decrease in the viscosity of the mixture, which presented a lower viscosity than the cement slurry, indicating that there were no peaks of variation in the mixture's viscosity. These results are satisfactory because according to [29], two or more fluids are compatible when the rheological measurements of mixtures are between the readings of pure fluids.…”

Fundamentals of Plug Placement

“…A spacer should have the following characteristics: compatible with a given type of drilling fluid or milling fluid, including bentonite muds and polymer based muds. The spacer properties should not affect the cement slurry viscosity nor changing the pumping time; to tolerate high solids and mud cake; to tolerate addition of wetting agents, dispersants, friction reducers, and retarders; low-fluid-loss properties; and permitting turbulence flow regime at low pumping rates for efficient mud removal [10][11][12][13][14]. Although spacers are used to remove drilling fluid and mud cake but it is unlikely to remove the mud cake without using mechanical aids.…”

“…Spacers are designed to improve cement bonds by water-wetting the cement-pipe or cement-formation interfaces while not destabilizing any sensitive zones and not adversely affecting the mud or cement properties [33]. In order to obtain an improved mud removal, studies show that density of displacing fluid should be at least 10% heavier than the displaced fluid, and the friction pressure of the displacing fluid should be greater by at least 20% than the displaced fluid [13]. The maximum mud removal occurs when the viscosity profile of spacer systems is higher than the viscosity profile of the drilling fluid and lower than the cement slurry.…”

Nowe rodzaje cieczy przemywających osady z płuczki inwersyjnej przed zabiegiem cementowania otworów wiertniczych

“…Mikroemulsję stanowi faza środkowa, która zawiera praktycznie całkowitą ilość surfaktantu oraz większość oleju i wody. Kolejne dwie fazy (w zależności od względnych gęstości): górna i dolna -zawierają pozostałą ilość oleju i wody, d) Windsor IV -układ stanowi pojedynczą fazę transparentnej mikroemulsji [1,2,10,13].…”