Heavyweight Magnetite as a Novel Weighting Material for Cementing HPHT Formations

Abstract

ABSTRACT The development of cement slurry with specified qualities, such as high density, is necessary to overbalance the high-pressure formations while cementing deep and ultra-deep oil wells. Hematite is now primarily utilized as a weighing material in oil fields, although its use raises several operational and environmental issues. The creation of a non-elastic cement matrix and cement segregation are the two most frequent problems associated with using hematite as a weighing ingredient. This study examined the effectiveness of using magnetite as a weighing component when cementing a deep production casing at a depth of 15,000 feet. The magnetite used in this study has a particle size of 18.84 μm and is composed of more than 99% iron. In-depth laboratory research was done on the performance of 18.0 ppg hematite- and magnetite-weighted cement slurry. In this work, the qualities of cement segregation, compressive and tensile strength, porosity and permeability, and elastic properties were investigated. This study demonstrated that using magnetite instead of hematite as a cement-weighting material might be successful. The density of the created magnetite-based cement system varies very slightly along the depth of the well, with only a 7.3% difference between the top and bottom of the cement. Both the casing and the drilled formations may be supported by the magnetite-based cement's high compressive and tensile strengths of 65.1 and 8.1 MPa, respectively. Additionally, impenetrable, the cement system created with magnetite has a permeability of only 0.003 mD. The capacity of the Magnetite-based system to lower the Poisson's ratio and boost cement elasticity, which is highly essential, especially for very deep wells, was confirmed when Poisson's ratio for the system created in this work was compared with that of hematite-based. INTRODUCTION Weighting materials are used to increase the drilling fluid's density to successfully balance the higher pressures in deep wells (Caenn et al., 2011; Hossain & Al-Majed, 2015; Stroud BK, 1922, 1926). When dealing with unbalanced wellbores, deformable/plastic formations, and high pore pressures, high mud weight above 18 ppg can be utilized, and cement samples of equivalent weight should be used (Magarini et al., 1999). The well may never produce its most total capacity without effectively isolating problematic zones (Nelson, 1990). Primary oil-well cementing procedures are carried out to meet various goals, including inhibiting fluid communication and flow between drilled formations and the wellbore, shielding the casing from acidic liquid attack, and supporting the casing (Mitchell & Miska, 2011).