Abstract
High-temperature conditions drastically compromise the physical properties of cement, especially, its strengths. In this work, the influence of adding nanoclay (NC) particles to Saudi class G oil well cement (OWC) strength retrogression resistance under high-temperature condition (300 °C) is evaluated. Six cement slurries with different concentrations of silica flour (SF) and NC were prepared and tested under conditions of 38 °C and 300 °C for different time periods (7 and 28 days) of curing. The changes in the cement matrix compressive and tensile strengths, permeability, loss in the absorbed water, and the cement slurry rheology were evaluated as a function of NC content and temperature, the changes in the structure of the cement surfaces were investigated through the optical microscope. The results revealed that the use of NC (up to 3% by weight of cement (BWOC)) can prevent the OWC deterioration under extremely high-temperature conditions. Incorporating more than 3% of NC severely damaged the cement matrix microstructure due to the agglomeration of the nanoparticles. Incorporation of NC particles increased all the cement slurry rheological properties.
Highlights
The main functions of the primary cementing in oil wells is to provide the desired mechanical stability, prevent any communication between the drilled formations by preventing the cement/formation annulus being present, protect the casing from being contacted by the formation of corrosive fluids so no microcracks should be present in the cement sheath, and prevent the fluids from flowing up toward the surface through the cement/formation annulus, microcracks in the cement sheath, and/or casing/cement annulus
The aim of this study is to evaluate the applicability of adding different percentages of NC with and without 35% BWOC of silica flour (SF) particles to Saudi class G oil well cement (OWC) to enhance its compressive strength under high-temperature conditions (300 ◦ C) encountered in geothermal environments and in wells experience cyclic steam injection
Incorporating NC into the cement formulation improved its tensile strength linearly under high-temperature conditions, which is a result of the accelerated hydration process
Summary
The main functions of the primary cementing in oil wells is to provide the desired mechanical stability, prevent any communication between the drilled formations by preventing the cement/formation annulus being present, protect the casing from being contacted by the formation of corrosive fluids so no microcracks should be present in the cement sheath, and prevent the fluids from flowing up toward the surface through the cement/formation annulus, microcracks in the cement sheath, and/or casing/cement annulus In these kinds of operation, the wellbore/casing annular space is filled by one or more cement slurries which must form strong enough and durable cement matrix to meet the needed isolation efficiency throughout the well life without the need for any minimal corrective interventions. The effect of the temperature on both the liquid phase when the slurry is pumped through the casing/wellbore annular space, and on the solid phase (hydrate cement) when the cement matrix is required to meet the physical and chemical properties considered when the cement program is designed, was earlier addressed by different studies [2,3,4,5,6,7].
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