In this research, an enhancement in lubricating, rheological, and filtration properties of unweighted water-based mud is fundamentally investigated using XC polymer NPs with 0.2gm, 0.5gm, 1gm, 2gm, and 4gm concentrations. Bentonite, that had been used in the preparation of unweighted water-based mud, was characterized using XRF-1800 Sequential X-ray Fluorescence Spectrometer, XRD-6100/7000 X-ray Diffractometer, and Malvern Mastersizer 2000 particle size analyzer, respectively. Lubricating, rheology and filtration properties of unweighted water-based mud were measured at room temperature (35°C) using OFITE EP and Lubricity Tester, OFITE Model 900 Viscometer, and OFITE Low-Pressure Filter Press, respectively. XC Polymer NPs show a good enhancement in lubricating, rheology and filtration properties of unweighted water-based mud. The effect of XC Polymer NPs on lubricating properties was denoted at 4gm concentration, where the reduction percentage in COF was 30%. An increase in PV, YP, AV, gel strength of unweighted water-based mud was obtained due to the addition of XC Polymer NPs at concentrations up to 4gm. A reduction in filtrate volume and mud cake thickness of unweighted water-based mud was obtained due to the addition of XC Polymer NPs at 2gm and 4gm concentrations, the best result was obtained with using 4gm concentration, the reduction percentage of filtrate volume was 20.7% and mud cake thickness was 41%.
Managing lost circulation during drilling is a great challenge issue in naturally fractured or vugy formations. This situation becomes further complicated if there are gas or oil returns at the same formation or at a formation above it. The lost circulation problem happens in some of the northern Iraqi oil fields such as Khabaz oil field. Particulate lost circulation materials (LCM) have been used for many years to control lost circulation. However, these traditional LCMs are not efficiently applicable to cure sever to total losses, such as highly fractured formations and formation with large vugs. In this work, an experimental attempt was done to solve such problem in Khabaz oil field. The experiments were carried out using a closed loop circulation system that simulates the drilling fluid loss into formations. Five core plugs from Azkand formation of Khabaz oil field from different depths were used. The experiments were grouped into three, the first was done with the fresh-water-based drilling fluid to measure the severity of losses. The second, fresh-water-based drilling fluid was treated with traditional LCM (cotton seeds) to investigate how the severity of losses is affected by these materials. Adding polymer lost circulation material were the last sets to modify the drilling fluid rheological properties which prepare a medium within the lost circulation zone that increases the friction inside the losses paths to increase the LCMs (the polymer itself) sealing efficiency.
In oil and gas industry, the nanotechnology has been applied in different fields. Reservoir, exploration, drilling, completion, production, processing, and refinery are nanotechnology applications fields. Nanoparticles materials are one of the areas that are utilized in preparing drilling fluids. These nanomaterials are used to formulate high performance drilling fluids. In other words, these nano particles materials can be used to design smart drilling fluids. The properties of these drilling fluids can be met the well conditions requirements. The aim of this study is to enhance the performance of Iraqi bentonite in drilling fluids using nanomaterials. Iraqi calcium montmorillonite clay (Ca- bentonite) from Wadi Bashera in Iraqi Western Desert was obtained and studied in order to use it as an alternative active solid to the imported commercial bentonite. Water based drilling fluids were prepared with 3, 6, and 12 wt. % of Iraqi bentonite. Mgnesium oxide nanoparticles (MgO NPs) and ferric oxide nanoparticles (Fe2O3 NPs) with different concentrations were used. The experimental work showed that, MgO NPs resulted in a significant increase in the rheological properties of drilling fluids prepared with 3 and 6 wt. % of Iraqi bentonite. In contrast, moderate effect on the rheological properties of drilling fluid prepared with 12 wt. % of Iraqi bentonite were obtained with low concentrations of Fe2O3 NPs. Basically drilling fluids prepared with Iraqi bentonite had extreme filtrate volume compared with API specifications and poor controlling to filtration properties were obtained with MgO NPs and Fe2O3 NPs additions. The impact of these two nanomaterials was revealed on the stability of drilling fluids prepared with Iraqi bentonite, where an enhancemment from 65 % to 100% was observed.
During drilling operations, wellbore instability is one of the reasons that increase nonproductive time (NPT). Maintaining a stable wellbore is the primary importance during drilling by applying a proper geomechanical model to analyze and understand the distribution of stresses around the wellbore in order to minimize drilling risk and NPT. The lack of any geomechanical studies in Zubair oilfield in southern Iraq is one of the reasons that lead to wellbore stability-related problems and thus an increase in NPT. Petrel Geomechanics 2018 was used to show the distribution of the stresses and the mechanical properties. Showing the distribution of stresses in 3D MEM has big advantages in several ways, and one of them is to select the best path for any future directional wells. To mitigate wellbore stability problems and depending on the 1D mechanical earth models (MEM) results, a detailed 3D MEM was built for Zubair oilfield as the method to precisely pinpoint and diagnose those problems. The results of this study show two points; first is an abnormally pressured zone in Tanuma shale formation, and second, a narrow mud weight window in front of the Tanuma formation. As a conclusion, the mechanical earth model was an efficient tool in diagnosing and predicting geomechanics-related problems, thus suggesting an alternative mud weight program for the problematic zone, which is more important to reduce the most essential factor in the NPT.
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