Nanomaterials are the new additives for drilling fluids that can improve its properties and eliminate problems due to increased downtime and well costs. The objective of this research is to select the optimum concentration of nanoparticles that enhance drilling fluid properties and hydraulics. This study investigates the effects of commercially available nanoparticles on the rheological and filtration properties and optimizes the hydraulics of water-based drilling fluids. In this study, the samples were prepared as water-based muds with and without various concentrations of 5.7 nm colloidal silica dioxide nanoparticles. Series of laboratory experiments were carried out for all samples using standard API Low Pressure Low Temperature (LPLT) filtration and rheological tests. Two mud systems at different pH conditions were used to evaluate the impact of nanoparticles. A commercial software was used to evaluate the impact of the nanoparticles on the Equivalent Circulation Density (ECD) and the circulation pressure loss in a deviated wellbore. Results show enhancements in the rheological and filtration properties for water-based muds treated by the nanoparticles used in this study with concentrations below 0.7% by weight. Furthermore, the results show the ability of these nanoparticles to make the filter cake consistent, compacted, and thin. The results reflect the negative impact of the nanoparticles with concentrations above 0.7% by weight on some of the rheological properties. The optimum nanomaterial concentrations with the best properties were observed as (0.1%-0.3%) by weight. Furthermore, the concentration of 0.1% by weight reflected the significant reduction in the ECD and the circulating pressure loss. Nanoparticles used in this research can play a vital role in reducing drilling problems. Multilateral wells, slim holes and deep horizontal wells can be drilled by using water-based mud with the addition of proper nanoparticles and eliminating the need for oil-based muds that are expensive and environmentally unacceptable. However, it is critical to select the proper size and concentration of nanoparticles in order to eliminate its negative impact on the drilling fluid properties.

Today applications of drilling require proper identification of operations where a cost reduction is possible. Many indicators are present when one tries to optimize the drilling operations such as casing size and mud properties. On the other hand the selection of the optimum bit requires information from a variety of sources. The parameters affecting the bit performance are complex and their relationship is not easily recognized. The general trend is to evaluate the performance of the bit from an offset well. A new methodology was developed to model the rate of penetration and bit wear under various formation types and operating parameters. This method introduces a new approach with improved bit wear prediction. A simulator was used to generate drilling data to eliminate errors coherent to field measurements. The data generated was used to establish the relationship between the complex patterns such as weight on bit, rotary speed, pump rates, formation hardness, and bit type. The method was tested using data from runs conducted with a rig floor simulator. The validity of the proposed method was also demonstrated with data from an existing field. Introduction The success and hence the economics of a drilling operation depends on the condition of the bit. With bits performing at high penetration rates, the well drilling costs can be lowered. Thus, the selection of a proper bit type and the operating parameters are important challenges one faces during the drilling operations. Work performed by several investigators have shown that many bit and fluid components affect the penetration rates. Different methods can be utilized in the optimization of drilling. Researchers proposed the use of empirical correlations and predictive techniques. In these approaches either laboratory data were used to derive the empirical correlations or offset well data was used to fine tune the predictive method. Neural Networks. Neural networks have been successfully used in different fields due to their capability to identify complex relationships when sufficient data exist. Recently, they have been successfully applied to different areas of petroleum engineering such as multi-phase pipe flow, reservoir characterization, production, and drill bit diagnostics. The neural network developed to diagnose the drill bit used six parameters consisting of lithology (or formation type), torque, rate of penetration, weight on bit, rotational speed, and hydraulic horsepower per square inch of nozzle as input. The network was trained to predict the bit wear as output. The use of formation type or lithology introduces errors for conditions where the predicted formation types and depths differ from the predicted properties. Although the drill bit diagnosis network was successful it was based on laboratory data and did not cover all formation hardness and bit grade levels, thus limiting its applicability. In this study, we introduce a new approach to predict a drilling parameter such as the rate of penetration by designing a new neural network. Approach A new methodology is introduced to predict the ROP values during drilling. This approach uses the measured data to determine the relationship between several parameters like bit type, weight on bit, depth, and rotary speed recorded during the drilling operations. Two different data sets were used in this study. The first data set consisted of approximately 8,000 measurements taken at selected wellbore conditions. The rig floor simulator available in the departmental facilities were employed for this purpose. The use of simulated data provided additional insight in terms of parameters like formation abrasiveness, bit tooth wear, and bit bearing wear as a function of drilling time that are commonly not possible to measure in the field. The second data set consisted of approximately 500 measurements from several wells in the United States. Simulated Data. Runs were conducted using a rig floor simulator and data were continuously recorded until bit fails either due to bearing wear or tooth wear. The data set contained approximately 8,000 measurements taken at predesigned wellbore conditions. The simulated data were chosen in this study to eliminate errors inherent to data acquired in the field. Table 1 shows the recorded data types and their range. P. 175^

Increased demand for energy resulted in the expansion of drilling activities worldwide. Any improvement in terms of well planning and drilling operation can result in significant savings for the operator. A good plan includes all information from offset wells as well as sound engineering principles and it relies on subsurface characteristics and operating conditions. While formation properties are not controlled by drilling, the operational parameters can be modified to improve the drilling operation on a real time basis. Thus it is important to study the operational factors affecting the performance of a rig. Particularly, understanding the parameters that control wellbore cleaning is beneficial in both horizontal and deviated wells. In this study, a section of casing-drill pipe annulus section was simulated using Computational Fluid Dynamics (CFD) to determine the effects of different parameters such as fluid velocity, cutting size, rate of penetration, drill pipe rotation and inclination angle in deviated wells. The simulations were conducted at steady state and the results for maximum cutting concentrations in the annulus were analyzed. Formation of cutting beds is noticed near the entry section of the annulus and the transport of the cuttings in the annular section occurred in the form of stratified flow. Fluid flow rate, angle of inclination and rate of penetration have a major impact on cutting concentrations and proper prediction of these parameters are important to avoid formation of cutting beds. It is also noted that drillpipe rotation can enhance cutting transport but it generally has a greater effect on smaller sized particles. Introduction As horizontal wellbores get longer and deeper, and as practices such as extended reach drilling become more common, hole cleaning can be an increasingly difficult and different challenge from vertical wells. In an inclined well, cuttings settle vertically, but the fluid velocity has a reduced vertical component. Particles settle quickly and have less distance to travel before they hit the borehole wall. Here, the velocities are negligible and particles tend to deposit in the annulus leading to the formation of contiguous beds. Significant reduction of transport capacity occurs in horizontal wells. Inefficient hole cleaning and formation of beds lead to problems such as premature bit wear, high torque and drag, stuck pipe and slow drilling rates which increase drill time and costs. The major parameters which affect hole cleaning in an annulus can be divided into three different groups. The first group consists of the fluid parameters such as fluid density, fluid viscosity and fluid flow rate. The second group consists of cutting parameters which include cutting density, cutting shape and size and cutting concentration. The third group consists of the operational parameters i.e. the angle of inclination, pipe rotation speed and eccentricity in the hole. Research into these cutting transportation parameters and their effects can lead to prediction of carrying capacity of fluids and therefore facilitating the optimum design of directional wells. Real time data from on site locations is impossible to collect and analyze with cutting transport parameters. Hence, researchers[1,2,3,4] started building large scale flow loops to conduct experiments to observe and investigate the variables that affect cutting transportation. The observations of these experiments suggested the existence of different flow patterns based on the hole cleaning parameters. Cutting transport problems in horizontal conduits occur only when moving bed or stationary-moving bed patterns are observed. The parameter values that lead to bed formations are the ones that are of importance and the ones that are studied in the literature. These experimental works mostly give us general correlations and rules of thumbs (ranges of parameters) to avoid the formation of the bed.

As sensitive and electro-chemically active additives, anionic nanoparticles can be used to develop various water-based mud designs to fulfill different drilling conditions with less costs. For an optimum performance, however, they must be carefully selected and formulated. The objective of this study was to compare and evaluate various properties of water-based nanomuds. This was achieved by investigating the impact of very low concentrations of commercially affordable three types of negatively charged nanoparticles on the rheological, hydraulic and filtration properties of a high pH "flocculated" water-based mud. Simultaneously, the superior and insufficient types and concentrations were explored. In this research, four concentrations of each of anionic nanosilica, nanotitanium, and nanoaluminum were used to treat the high pH (11.5-12) water-based mud. Sequences of API experimental tests were conducted by using standard Low Pressure Low Temperature (LPLT) filtration and rheological devices for all samples. For the hydraulic evaluation, a commercially available software was used to simulate the impact of the nanoparticles on the equivalent circulation density (ECD) and the drillpipe circulation pressure in a typical directional well. The results show significant improvements in the rheological and hydraulics properties of the flocculated water-based muds treated by 0.1% wt. or less of nanosilica and 0.3% wt. or less of nanotitanium and nanoaluminum. For the higher concentrations, no more improvements were obtained. Further, the results show the ability of nanosilica and nanotitanium to reduce the filtration volume and no filtration reduction based on nanoaluminum. However, all the nanoparticles enhance the mudcake structure, but differently, and prevent the spurt water loss completely. The current nanoparticle types can be used to develop a qualified mud design, thereby reducing drilling problems, such as stuck pipe, formation damage, wellbore instability, downhole equipment failure, mud circulation loss, and shale swelling if they are properly formulated. Thus, the more complicated wells can be drilled by using water-based nano muds and by eliminating the high costs and bad environmental impacts of using oil-based muds.

Destabilized asphaltenes cause serious problems by precipitating in the reservoir pores which reduces the oil flow by decreasing the reservoir porosity and permeability significantly. This study investigates the impact of clays and salinity on the stability of asphaltenes for five different crude oil samples. First, both n-pentane and n-heptane insoluble fractions of five crude oils were examined under microscope after the interaction with water, brine, and porous media. The porous media was prepared with clay only, sand only, or sand-clay mixture. A monovalent (NaCl) and a divalent (CaCl2) salts at 0.2% and 4% concentrations were used to prepare brine samples. The systematic microscopic imaging conducted on asphaltenes show that both n-pentane and n-heptane asphaltenes are getting dispersed in water phase. However, this dispersion is hampered with the existence of ions in water and this impact increases with the increase in brine concentration. Nevertheless, the destabilization of asphaltenes is more pronounced with the presence of clays. Because the destabilized asphaltenes are precipitated in porous media, asphaltenes precipitation impacts the wettability of porous media. Hence, the wettability of oil-water-rock and oil-brine-rock systems was determined through water-air contact angle measurements. The pseudo reservoir rock-oil-water/brine systems were prepared by keeping constant the weight of each component in the system for five crude oil samples. Reservoir rocks were prepared by mixing sand and clay. The brine was prepared either with NaCl or with CaCl2. The impact of salt concentration on wettability was tested for both 0.2% and 4% brine solutions. It has been observed that the asphaltenes fraction has an important role on wettability determination, however, the interaction of asphaltenes with deasphalted oil is the main contributor which defines the wettability of the system. Thus, our systematic analyses on asphaltenes should be extended and similar analyses should be conducted on the deasphalted oil fractions.