Drilling fluid must fulfill various functions with a great impact on the drilling performance. Drilling fluid invasion can cause formation damage. Good quality mudcakes can prevent such damage. This research focuses on the lab techniques and performance results of testing innovative water-based drilling fluids containing nanoparticles (NPs) for minimizing formation damage at high-pressure/high-temperature (HP/HT) conditions. A couette type viscometer was used to examine the rheological properties of the drilling fluids tested in this research. Zeta potential measurements were conducted at different temperatures and concentrations to assess their stability and to investigate the role of charge potential. Indiana limestone outcrops were examined as the filter media for both static and dynamic filtration (up to 350°F and 500 psi) using a HP/HT dynamic filter press. The mudcakes were investigated using a computed-tomography (CT) scan, and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS). Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) was used to measure the concentrations of key ions in the filtrate fluids.A significant reduction in the filtrate fluid volume was achieved when using ferric oxide NPs (-43% for 0.5 wt%) compared to that of the base fluid. However, adding silica NPs led to an increase in the filtrate volume and mudcake thickness. Increasing the NP concentration resulted in an increase in the fluid loss and mudcake thickness. The mudcakes consisted of two layers, as indicated by the CT scan analysis. 0.5 wt% was found to be the optimal NP concentration, which provides less agglomeration and a reduction in the mudcake permeability by Ϫ76.4%. At this concentration, the ICP-OES analysis showed a higher cation dissociation, which promoted the formation of a different clay platelet microstructure. At a higher NP concentration, a new layer of NPs was formed in the mudcake, which adversely affects the mudcake characteristics, as demonstrated by CT scan analysis and SEM-EDS elemental mapping. The rheological measurements indicated a good rheology at different temperatures and NP concentrations. Moreover, the NPs helped to stabilize the viscosity and yield stress at high temperatures (up to 200°F). Aging at 350°F for 16 hours showed that NP-based drilling fluids remain stable with minor changes in rheological properties. The obtained rheological data for various NPs is fitted to the classical drilling fluid rheological models to determine the best fit-model, which can then be applied to an efficient design.This research provides a comprehensive evaluation of improved water-based drilling fluids, using ferric oxide and silica NPs for HP/HT applications. The examined NPs have the potential to enhance drilling fluid properties, which provides more efficient drilling operations and less formation damage.

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Access to deeper oil and gas reservoirs in hostile environments necessitates improvement of existing drilling fluids. This work focuses on the lab techniques for developing, assessing and analyzing innovative water-based drilling fluids containing iron oxide (Fe 2 O 3 ) and silica nanoparticles (SiO 2 ).The fluid loss characteristics were examined both in an American Petroleum Institute (API) static filter press and in a High Temperature-High Pressure (HTHP) filter press under elevated pressures and temperatures (300 psi/250˚F). A computed-tomography (CT) scan was used for deep analysis of the filter cake. Scanning Electron Microscopy (SEM) was used to analyze the morphology of the filter cake as well as to give deep insights for their microstructure, the interfacial phenomena and the interaction between bentonite particles and the nanoparticles. Inductively Coupled Plasma (ICP) mass spectrometry was used to determine the quality of the produced filtrate. Zeta potential measurements were used to assess the stability of the developed suspensions. The changes in the rheological properties of the nanofluids were measured at HT conditions using a standard Fann type viscometer.Significant modifications have been observed with the addition of nanoparticles to the base fluid of water-bentonite suspension in rheological and filtration characteristics. The rheological analysis showed an increase of the yield stress and of the gel strength as the concentration of nanoparticles was increased. Both the API static and the HTHP filter press indicated a remarkable improvement in the fluid loss and filter cake characteristics for the samples containing iron oxide nanoparticles. For samples containing silica nanopowder, there was an adverse effect on the fluid loss characteristics with minor changes in the rheological profile.The filtration efficiency was reduced with the increase of the concentration of Fe 2 O 3 nanoparticles which was confirmed by CT scan measurements. Results revealed that 0.5% (w/w) is the optimal concentration for the Fe 2 O 3 nanoparticles, above which they form a new layer in the filter cake that adversely affected the fluid loss and filter cake characteristics. SEM and ICP measurements confirmed this phenomenon and revealed the agglomeration effect and the smooth surface of the produced filter cakes. Zeta potential measurements at different concentrations and temperatures of the produced nanofluids showed that the iron oxide nanoparticles were stable in colloidal suspensions, whereas silica nanopowder was unstable under different temperatures.The examined nanoparticles have the potential to significantly improve the characteristics of the filter cakes at both low temperature-low pressure (LTLP) and HTHP conditions. They also have the ability to maintain optimal rheological properties so that many drilling problems can be efficiently mitigated. Their low concentration in the drilling system, compared to other conventional drilling additives, provides a basis for more efficient drilling practices.

As high-pressure/high-temperature (HP/HT) drilling is inherently expensive, drilling fluids and technologies should be carefully selected to successfully handle the associated challenges. Over the past few years, nanoparticles (NPs), among other additives, have been investigated to address these challenges. The objective of this study is to investigate the potential of using ferric oxide NPs on the filter cake properties in downhle drilling environments. Having an efficient filter cake is an important property of the drilling fluid and can affect the success of drilling operations. This research focuses oncharacterizatingthe filter cakes produced by Ca-bentonite-based drilling fluid contains ferric oxide NPs at downhle conditions. A combination of computed-tomography (CT) scan and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was used in filter cake characterization. The effect of NP concentration, fluid preparation method, and filtration condition were studied. A HP/HT filter press was used to perform the filtration process at conditions up to 350°F and 500 psi. Indiana limestone core disks were used to simulate the filter media. The experimental results showed that the ferric oxide NPs improve the filter cake and filtration properties of Ca-bentonite-based drilling fluid in the presence of polymer and other additives. Low NP concentration is preferred for obtaining a good cake quality with the best characteristics obtained at 0.3–0.5 wt% NPs. Furthermore, this drilling fluid can withstand conditions up to 500 psi and 350°F. Cake properties of 0.151 in. thickness, 6.9 ml filtrate volume, and 0.428 µd permeability was obtained at such conditions. The addition of NPs to the drilling fluid improved the filter cake properties under both static and dynamic filtration. SEM-EDS analysis confirmed the efficiency of using NPs to form a smoother/less porous filter cake morphology. Moreover, sonication for one hour and hydration for 16 hours are recommendedfor better preparation of these fluids. This research provides an experimental evaluation of using ferric oxide NPs with Ca-bentonite-based drilling fluid to produce high-quality filter cake at downhole conditions. The characteristics of the filter cake gererated confirmed the efficiency of such fluids.

Artificial intelligence (AI) and machine learning (ML) are transforming industries, where low-cost, big data can utilize computing power to optimize system performance. Oil and gas (O&G) fields are getting mature, where well integrity (WI) problems become more common and field operations are now more challenging. Hence, they are good candidates for transformation due to the low cost of data storage, highlighting the oil market decline, along with dynamic risk posed during operations. This paper is presenting a comprehensive compilation of different ML applications in diverse disciplines of the petroleum industry. The pool of AI and ML with respect to different areas of applications along with publication years has been categorized. The main focus of this study is classifying well integrity failures where the authors found that the potential of AI and ML in predicting well integrity failures has not been efficiently tapped, and there is an explicit gap in the literature. First, the applications of AI, ML, and data analytics in the O&G industry are discussed thoroughly, so this paper can be a comprehensive reference for readers and future researchers. Then data preprocessing is explained. This includes data gathering, cleaning, and feature engineering. Next, the different ML models are compared and discussed. Finally, model performance evaluation and best model selection are described. This study would be a concrete foundation in the design and construction of ML programs that can be deployed for WI risk management. The developed model can be simply used for any well stock, providing quick and easy assessment instead of subjective and tedious assessment. The layout can be simply adjusted to reflect the risk profile of any well type or any field.

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Summary One of the important functions of drilling fluids is to form a filter cake, which minimizes leakoff of drilling fluids into the formation. Drilling-fluid invasion can cause formation damage, but good-quality filter cake can reduce such damage. This research focuses on the laboratory techniques and performance results of testing innovative calcium-bentonite-based drilling fluids containing nanoparticles (NPs) for minimizing formation damage during drilling in harsh environments. A rotational viscometer was used to measure the rheological properties of the tested fluids. ζ-potential measurements were conducted at different NP concentrations to assess their stability and to investigate the role of charge potential. Indiana limestone outcrop disks were examined as the filter media for both static and dynamic filtration (up to 350°F and 500 psi) using a filter press. The filter cakes were examined using a computed-tomography (CT) scan and scanning-electron-microscopy energy-dispersive spectroscopy (SEM-EDS). Inductively coupled plasma optical-emission spectrometry (ICP-OES) was used to measure the concentrations of key ions in the filtrate fluids. A reduction of 43% in the filtrate-fluid volume was achieved when adding 0.5 wt% of ferric oxide NPs compared with that of the base fluid. However, using silica NPs led to an increase in the filtrate volume and filter-cake thickness. Using 0.5 wt% of ferric oxide NPs provided less agglomeration and reduced the filter-cake permeability. In addition, the SEM-EDS and ICP-OES analysis showed a replacement of the cations dissociated from the bentonite by NPs, which promoted the formation of a rigid clay-platelet structure. The produced filter cakes consisted of two layers, as indicated by the CT-scan analysis. Increasing the concentration of NPs resulted in an increase in the fluid loss and filter-cake thickness. At a higher NP concentration (2.5 wt%), a third layer of NPs was observed, which adversely affected the filter-cake characteristics, as demonstrated by CT-scan analysis and SEM-EDS elemental mapping. Furthermore, the NP-bentonite fluids had stable rheological properties at different temperatures (up to 200°F) and NP concentrations. In addition, aging these fluids at 350°F for 16 hours showed minor changes in the rheological properties. This research work provides an experimental evaluation of improved calcium-bentonite-based fluids using NPs under downhole conditions. The ferric oxide NPs have the potential to enhance the properties of calcium bentonite, as a low-cost alternative, to perform well in an application where the higher-value sodium bentonite is commonly used, which could provide more-efficient drilling operations and less formation damage.

Summary During the past few decades, nanoparticles (NPs) have been investigated as additives to address the challenges of drilling fluids and have shown potential for application. The present work focuses on introducing and investigating a calcium (Ca) bentonite-based drilling fluid with ferric oxide (Fe2O3) NPs. Generating efficient filter cake is an important property of the drilling fluid and can affect the success of the whole drilling operation. This study aims at characterizing the filter cake produced by Ca bentonite-based drilling fluid modified using Fe2O3 NPs. Computed-tomography (CT) scan and scanning electron microscopy energy dispersive spectroscopy (SEM-EDS) were used for filter-cake characterization. The effects of NP concentration and filtration conditions on the filter-cake properties were investigated. A high-pressure/high-temperature (HP/HT) American Petroleum Institute (API) filter press was used to perform static and dynamic filtrations. Indiana limestone disks were used as filter media to simulate formation behavior. The modified Fe2O3 NPs/Ca bentonite fluid showed improved filter-cake and filtration properties in the presence of polymers and other additives. A concentration of less than 1 wt% of NPs is preferred for generating a good-quality filter cake. The best characteristics were obtained when using an NP concentration of 0.3 to 0.5 wt%. The NPs/Ca bentonite-based drilling fluid can withstand conditions up to 500 psi and 350°F and generate filter-cake properties of 0.151-in. thickness, 6.9-cm3/30-min filtrate volume, and 0.449-µd permeability. Fe2O3 NPs improved the filter-cake properties under both static and dynamic conditions. SEM-EDS showed a smoother/less-porous filter-cake morphology with less agglomeration when using NPs at optimal concentrations, which confirms that the NPs play a key role in forming a better filter-cake structure. The present work provides an experimental evaluation of the filter cake generated by modified NPs/Ca bentonite-based drilling fluid at downhole conditions, which is an extension of our previous work using a simple NPs/Ca bentonite suspension (Mahmoud et al. 2018). The improved properties of the filter cake confirmed the effectiveness of using Ca bentonite modified with Fe2O3 NPs to formulate a drilling fluid that can effectively be used for drilling practices.