Fluid Loss Properties Research Articles

Impact of zinc oxide nanoparticles on the rheological and fluid-loss properties, and the hydraulic performance of non-damaging drilling fluid

Exploration of shale gas has indeed changed the dynamics of the petroleum industry. Efficient drilling in shale bearing zones largely depends on the nature of drilling fluid that are used. Non-damaging drilling fluid (NDDF) has emerged as an important class of drilling fluids over the last decade due to its superior inhibitive nature that yields better wellbore conditioning, especially in formations where the shale content is very high. However, the thermal stability of this biopolymer-based drilling fluid has posed limitations in its application in moderate to high-temperature wells. This research presents comprehensive rheological, fluid-loss and computational fluid dynamics (CFD) analysis to study and quantify the effects of zinc oxide nanoparticle (ZnO NP) on the NDDF. It was found that ZnO NP enhances thermal stability by yielding a viscosity over 300% than that of the base NDDF at 80 °C. These NPs also induces viscoelastic solid property that nurtures superior gel forming and thixotropic ability. Furthermore, more than 80% the viscous structure is regained within a timeframe of 180 s with the addition of 0.8 and 1 wt% ZnO NP as compared to 44% for the base NDDF. With the addition of 1 wt% ZnO NP the operating temperature of NDDF reaches up to 100 °C. Besides, fluid-loss of NDDF is reduced by 49% with doping of 1 wt% ZnO NP in NDDF. CFD simulations show excellent cutting carrying capacity of ZnO NP NDDFs with 1 wt% concentration showing a reduction in cutting retention by 29.13% at high temperatures (80 °C). Furthermore, the velocity profile showed that skewness in case of ZnO NP NDDF is reduced, indicating a better sweep of cuttings in the annular region. Despite exhibiting viscoelastic properties, the pressure drop of ZnO NP NDDFs along a complex wellbore geometry was within an acceptable range, ensuring flowability.

Evaluating the Effect of Drying Methods on the Properties of a Water Base Drilling Mud

It is important to understand the properties influencing the efficiency of a drilling fluid while drilling for oil and gas. As a result, drilling fluid must be designed in order to comply with three important requirements which are easy to use, cost effective and being environmentally friendly. Several studies have been carried out on the use of local materials as suitable substitute for imported additives. This study focuses on the use of starch processed from local cassava (<i>Manihot esculenta Crant</i>), (TME 419) using the process of wet milling and dried using three different methods namely: oven drying, direct heating and sun drying Due to this short coming resulting from the use of native starch, the starch was chemically modified using the process of esterification before being used as additive for treatment of the water-based drilling. The mud samples were prepared using Wyoming bentonite and distil water as the base fluid. Varying concentration of additives (0.5, 1.0 and 1.5 g) were added to the different mud samples and the laboratory test carried out in accordance with the API Recommended Practice 13B at varying temperatures (30, 50.70 and 90°C). The various mud samples rheological properties was determined using a Fann35A rheometer and the filtration properties using a low –Temperature and High –Pressure API Filter Press at 100 psi with a 3.5” filter paper. The mud samples labelled labeled A, B and C were treated with oven dry, direct heat and sundry modified starches, respectively. While two control mud samples were prepared using low viscous Carboxymethyl cellulose for mud sample D and extra high viscous CMC in sample E. Although the Viscosity and fluid loss profiles result of the mud samples comparable performance with that of the commercial CMC’s. However, mud samples treated with oven dried starches presented the best results in their rheological as well as fluid loss properties

A high-temperature and High-Density Environmentally-Friendly Water-Based Drilling Fluids Based on Modified Plant Polyphenols

To improve the high-temperature resistance and density upper limit of environmentally friendly water-based drilling fluids, the fluid-loss reducer EHT-FL and the thinner EHT-TH were developed by modifying plant extracts of natural polyphenol. Two synthesized products were characterized by infrared spectroscopy. In laboratory experiments, the fluid-loss reducer EHT-FL and the thinner EHT-TH exhibited good high-temperature resistance. And the EC50 reached 2.38×105 mg/L and 4.49×105 mg/L, respectively, with no biological toxicity. The medium-pressure and high-temperature/high-pressure fluid-loss of freshwater-based mud with 2.0% EHT-FL are only 7.2 mL and 23.6 mL after aging at 200℃. When the dosage of EHT-TH is 1.0%, the apparent viscosity of high-density water-based drilling fluid (ρ=2.0 g/cm3) after aging at 200℃ decreases from 106.5 mPa·s to 66.5 mPa·s, and the high-temperature thickening phenomenon disappears. Based on the excellent temperature-resistance of EHT-FL and EHT-TH, a high-temperature and high-density (ρ=2.0 g/cm3) environmentally friendly water-based drilling fluid has been developed. This drilling fluid has reasonable rheological and fluid-loss properties. It has high-temperature resistance of 210℃ and resistance to 25% salt contamination, 1% calcium contamination, and 10% inferior soil contamination. EC50 of this drilling fluid is 4.19×104 mg/L, BOD5/CODCr is 29.23, heavy metal content is lower than the standard value, non-toxic, biodegradable. Therefore, this environmentally friendly drilling fluid can meet the drilling needs of deep-wells complex formations.

Improving the rheological and fluid loss properties of the water-based mud using wheat flour

This study aims to evaluate the effect of wheat flour as a natural and environmentally friendly material on the properties of water-based mud. Recently, many experiments have been conducted with various additives to improve the properties of drilling fluids. The effect of using wheat flour as a new additive to drilling fluid was studied to improve rheological and filtration properties. In the laboratory several samples of water-based mud were prepared, different concentrations of wheat flour from 1 wt% to 7 wt% were added to the mud and tested by using a Fann 35 viscometer, 140 Fann Mud balance, and an API LT-LP filter press. The results showed that adding 7 wt% of wheat flour was the optimal concentration. It was found that the apparent viscosity and yield point increased by 50% and 35%, respectively, when 7 wt% of wheat flour was added to the water-based drilling fluid. Likewise, the fluid loss rate was reduced by 25% when using the same concentration of wheat flour.

Prediction of Formation Damage, Fluid Loss and Rheological Properties of Water Based Mud with Corn Cob

The extent of damage to formation caused by water based drilling mud containing corn cob treated with sodium hydroxide to partially replace polyanionic cellulose (PAC) as a fluid loss control additive has been studied. Core samples were obtained from a well in Niger Delta for this study with a permeameter used to force the drilling mud into core samples at high pressures. Physio-chemical properties (moisture content, cellulose and lignin) of the samples were measured and the result after treatment showed reduction. The corn cob was combined with the PAC in the ratio of 25-75%, 50-50% and 75-25% in the mud. Analyzed drilling mud rheological properties such as plastic viscosity, apparent viscosity, yield point and gel strength all decreased as percentage of corn cob increased in the combination and steadily decreased as temperature increased to 200oF. Measured fluid loss and pH of the mud showed an increase in fluid loss and pH in mud sample with 100% corn cob. The extent of formation damage was determined by the differences in the initial and final permeability of the core samples. Experimental data were used to develop analytical models that can serve as effective tool to predict fluid loss, rheological properties of the drilling mud at temperature up to 200oF and percentage formation damage at 100 psi.

Prediction of Formation Damage, Fluid Loss and Rheological Properties of Water Based Mud with Corn Cob

The extent of damage to formation caused by water based drilling mud containing corn cob treated with sodium hydroxide to partially replace polyanionic cellulose (PAC) as a fluid loss control additive has been studied. Core samples were obtained from a well in Niger Delta for this study with a permeameter used to force the drilling mud into core samples at high pressures. Physio-chemical properties (moisture content, cellulose and lignin) of the samples were measured and the result after treatment showed reduction. The corn cob was combined with the PAC in the ratio of 25-75%, 50-50% and 75-25% in the mud. Analyzed drilling mud rheological properties such as plastic viscosity, apparent viscosity, yield point and gel strength all decreased as percentage of corn cob increased in the combination and steadily decreased as temperature increased to 200oF. Measured fluid loss and pH of the mud showed an increase in fluid loss and pH in mud sample with 100% corn cob. The extent of formation damage was determined by the differences in the initial and final permeability of the core samples. Experimental data were used to develop analytical models that can serve as effective tool to predict fluid loss, rheological properties of the drilling mud at temperature up to 200oF and percentage formation damage at 100 psi.

Influence of Weighting Materials on the Properties of Oil-Well Cement

The integrity of oil and gas wells is largely dependent on the cement job. Maintaining the properties of the cement layer throughout the life of a well is a difficult task, particularly in high-temperature and -pressure conditions such as those in deep wells. Cementing deep wells require slurries with high densities. Heavyweight cement systems are those designed with weighting materials. These materials have a higher specific gravity in comparison to cement. The purpose of this work is to investigate the influence of weighting materials on the properties of Class G oil-well cement and to make necessary recommendations for their use. The rheology, fluid loss, gas migration, and dynamic elastic properties of three cement slurries containing different weighting materials, namely, hematite, barite, and ilmenite, were studied. The results indicate that cement slurry designed with barite exhibits the best rheological behavior that would provide a perfect solution for deep wells where cement placement is a concern. The barite slurry had the lowest plastic viscosity. The plastic viscosity of the hematite and ilmenite-weighted systems was higher by 11.5 and 12.4%, respectively. The barite-based slurry also had the highest yield point of 84.3 lbf/100 ft2, whereas the yield points of hematite and barite cement were 37.9 and 29.5 lbf/100 ft2, respectively. Furthermore, the gel strengths of barite cement were the highest, with 10 s and 10 min gel strengths of 11.5 and 39.5 lbf/100 ft2, respectively. Ilmenite had the most positive impact on fluid loss control, which would be appropriate in high permeable formations. It had a fluid loss of 66 mL/30 min, lower than those of the hematite (80 mL/30 min) and barite (82 mL/30 min) systems. Furthermore, the best dynamic elastic properties were exhibited by the ilmenite system, with the smallest Young’s modulus (27.3 GPa) and the highest Poisson ratio (0.252). This would make the ilmenite to be very useful in developing heavyweight cement composites that could withstand severe external loads imposed on the casing and cement. The hematite cement was the most impermeable to gas migration, with a gas volume of 127.8 cm3, whereas the volume measured in the barite and ilmenite systems were 20.9 and 78% higher, respectively. This makes the hematite to be very useful in deep gas wells where gas migration control is important.

Synthesis and assessment of a hydrophobically associating heteropolymer in water-based mud

Water-soluble polymers can be used as key ingredients of both drilling fluids for virgin fields and polymer-enhanced oil recovery in underperforming reservoirs. The efficacy of hydrophobically associating heteropolymer (HAH-Polymer) as an agent for petroleum resource recovery was examined in this study. The hydrophobically associating heteropolymer (HAH-Polymer) comprising acrylamide, sodium 2-acrylamido-2-methylpropanesulfonate, hydroxyethyl methacrylate and lauryl methacrylate was synthesized in micellar medium by free-radical polymerization. The hydrophobically associating heteropolymer (HAH-Polymer) was characterised by FTIR and 1H NMR spectral analyses. The effects of temperature, pH and shear on the solution behavior of the HAH-Polymer were also examined. Rheological and fluid loss properties of HAH-Polymer-incorporated water-based drilling fluids were assessed. The HAH-Polymer improved the thermal stability between 25 and 160 °C of the drilling mud and maintained mud fluid loss of 8.4–8.6 cm3 compared with the polymer-free blank of 43.5–107.0cm3. In a salt-contaminated mud, the heteropolymer enhanced rheological properties and significantly reduced API filtration loss to 7.6–8.8 cm3 after hot aging between 25 and 150 °C. Under high temperature–high pressure filtration testing of muds, the HAH-Polymer demonstrated excellent fluid loss reduction by providing about eightfold fluid loss control (14.7 cm3) compared to the polymer-free blank (113.2 cm3) at 150 °C.

Salt-responsive zwitterionic copolymer as tackifier in brine drilling fluids

Salt contamination has become the most critical challenge faced by water-based drilling fluids (WDFs) under extreme salinity and high temperatures, which deteriorates rheology and fluid loss properties, causing drilling accidents such as leakage, formation collapse and borehole instability. Herein, we report a salt-responsive zwitterionic polymer (PAMN) and its novel application as a tackifier in brine drilling fluid exploiting the anti-polyelectrolyte effect, in which the zwitterionic polymer molecular chain has undergone a transformation from a collapsed small spherical shape to an extended chain shape corresponding to the increasing ionic strength of the electrolyte. Compared with the saturated brine drilling fluid, the apparent viscosity and plastic viscosity of the saturated brine drilling fluid dispersed with PAMN increased by 542.9% and 925% respectively owing to the charge interaction on the molecular chain of PAMN was shielded by sodium chloride electrolyte, which resulted in the increase of the radius of gyration (Rg) of the PAMN molecular chain. Additionally, the salt response mechanism of zwitterionic polymer PAMN had been revealed by molecular simulation technology, which simulated the radius of gyration, radial distribution function (RDF), mean square displacement (MSD) and energy of molecular chain in water and salt water, respectively. This work demonstrates that the approach can be extensively generalized to a large class of synthetic zwitterionic polymers and can promote the development of various salt-responsive intelligent drilling fluids.

Zero fluid loss, sensitivity and rheological properties of clay bentonite (WBM) modified with nanoclay quantified using Vipulanandan models

To improve the performance, sensibility, rheological properties, fluid loss of the bentonite water-based drilling mud (WBM), and minimizing the fluid loss of the WBM. The impact of bentonite modified with nanoclay (NC) on the sensibility, rheological properties, and fluid loss of the WBM was investigated. Depend on the information collected from different research studies, the percentage of bentonite in the WBM was ranged from 2%-8% as a percentage of the weight of water. The percentage of NC was ranged between 0 and 1% by mass of drilling mud. The tests were performed under various temperature conditions ranged between 25 °C and 85 °C. From the lab studies and numerical examinations, the electrical resistivity (ER) was identified as a sensing property of the WBM so that the rheological properties can be estimated during the construction. The additional 1% NC reduced the ER of the WBM by 15% to 36% depending on the composition of the drilling fluid and the temperature of testing. The nanoclay modification increased the yield stress (yield point) and shear stress limit tolerance of the WBMs measured using Vipulanandan rheological model by 32% to 60%, and the outcome of the model prediction was related with Vocadlo model. The laboratory HPHT fluid loss tests were conducted on the drilling fluids based bentonite modified with NC using an American Petroleum Institute (API) standard test up to 420 min until the end of the fluid loss. Zero fluid loss was obtained when 8% of bentonite drilling mud modified with 1% of NC at 25 °C. The Vipulanandan fluid loss model predicted the short and long-term fluid loss and the upper limit of fluid losses very well.

Controlling Shale Swelling and Fluid Loss Properties of Water-Based Drilling Mud via Ultrasonic Impregnated SWCNTs/PVP Nanocomposites

Wellbore instability due to shale swelling and fluid loss of drilling mud is the main challenge faced by the oil and gas industry. Herein, we successfully demonstrated the positive impact of newly developed single-walled carbon nanotubes/polyvinylpyrrolidone (SWCNTs/PVP) nanocomposites on the drilling efficiency of water-based muds (WBMs). By adopting a standardized sonication technique, we achieved highly dispersed and uniform distribution of single-walled carbon nanotubes (SWCNTs) within the matrix of polyvinylpyrrolidone (PVP). SWCNTs provided the required mechanical strength and hydrophobicity, while PVP acted as a binder, filler, and dispersion medium. The surface morphology of shales was compared before and after modification with SWCNTs/PVP nanocomposites. The moisture adsorption/repellent characteristics of the shales were predicted by Fourier transform infrared (FTIR) spectroscopy. The dispersion stability of synthesized SWCNTs/PVP nanocomposite with bentonite clay in the presence of water was also recorded for 24 h. The drilling mud modified with 5-SWCNTs/PVP nanocomposite demonstrates 23% reduction in fluid loss. The inhibition stability and swelling rate of shales were systematically investigated and compared with water, KCl, unmodified mud, and commercial shale inhibitor. The comparison indicates that the modified drilling mud having 5-SWCNTs/PVP composite showed the highest dispersion recovery (89.5%) and the lowest swelling rate (21.6%). The synthesized nanocomposite not only forms a protective layer on the shale surface to hinder the access of water but also offers structural stability to the drilling mud. Improved swelling inhibition, fluid loss control, and long-term stability of shale against reactive fluid, suggested that the modified WBM can be effectively utilized to control wellbore instability during drilling operations.

Beneficiation of Nigerian bentonite using local materials

In previous studies, it has been found that the Nigerian bentonite is deficient in terms of its fluid loss and rheological properties which includes yield point. Also, due to its high calcium content and low sodium content as opposed to foreign bentonite, it does not meet the API standard of drilling. This research was carried out to beneficiate the Nigerian bentonite as regards its fluid loss properties, rheological properties and wellbore stability. Snail shell is seen as waste substance in Nigeria, and Mucuna solannie on the other hand is a local major food supplement in Nigeria and is found in large quantities. The elemental and oxide compositions of the snail shell and Mucuna solannie were determined through scanning electron microscope and X-ray diffraction measurements, respectively. The additives were used to beneficiate the Nigerian bentonite, and the test result proved that at considerable concentrations of the additives, the Nigerian bentonite was able to compete with foreign bentonite and also met API specifications. Both additives contain high concentrations of nanoparticles and inhibitive calcium and potassium for wellbore stability. Beneficiated Nigerian bentonite also proved to be viable economically when compared with foreign bentonite.

Application of sustainable saffron purple petals as an eco-friendly green additive for drilling fluids: A rheological, filtration, morphological, and corrosion inhibition study

In this study, effects of dried saffron purple petals (SPP) powder were examined on the rheological, fluid loss, and corrosion inhibition properties of bentonite-based drilling fluids. Drilling fluids containing different amounts of the SPP powder were prepared and their rheological behavior was investigated via the rotary viscometry and rheometric mechanical spectroscopy (RMS). Rotary viscometer results were fitted with Power-law, Bingham plastic, and Herschel-Bulkley models and the obtained data were compared with that of the base mud. All models fitted the rotary viscometer data with the determination coefficients higher than 0.93. The presence of 3 wt% of the SSP in the fluid significantly improved the fluid’s yield stress and consistency index by 223.3% and 94.4%, respectively compared to those of the base mud. The filtration performance and cake formation results confirmed a 45% enhancement in the permeation barrier behavior of the fluid containing 3 wt% SPP powder. Electrochemical impedance measurements illustrated that the total impedance of the mild steel increase from 299 to 39,800 Ω cm2 in the presence of 3 wt% SPP powder compared to the control sample. Additionally, potentiodynamic polarization plots indicated a mixed-type inhibition mechanism for the SPP powder with the corrosion rate of 0.004 mm year−1 and inhibition efficiency of 96.5% in the presence of 3 wt% SPP powder. The morphology of mild steel plates immersed in SPP filled fluids demonstrated the formation of corrosion inhibitive layers on the metallic surface, which hindered the anodic and cathodic reactions while a considerable amount of rusts and corrosion products formed for the plate immersed in the base mud. Furthermore, having SPP as an organic green additive would leave no damaging effects on the surrounding environment and ecosystem.

Fluid Loss and Filtration Properties of a Citrus Sinensis Pectin Extract-based Drilling Mud

The production of drilling mud using pectin extracted from Citrus Sinensis peels was carried out. The extraction was carried out using water-hot acid technique which is a conventional method, and the extracted pectin was pre-gelatinized using calcium water. The pre-gelatinized pectin biopolymer was used to prepare drilling mud. Filter loss method was used to determine the filtration properties of the mud at 25°C and 200°C and 0.1g/mol concentration of pectin polymer was compared to the filtration behavior of hydroxyl propyl starch modified drilling mud. Our results showed that the pectin biopolymer mud (PPM) has better filtration control behavior than the hydroxyl propyl starch modified drilling mud (CMM). The study also showed that highest sorptivity value of 21.25 was obtained with PPM at 200°C, while the highest diffusivity value of 0.424 was obtained with CMM at 200°C. Keywords: Pectin, Citrus, Biopolymer, Sorptivity, Diffusivity, Drilling mud, Filtration DOI: 10.7176/CMR/12-3-03 Publication date: March 31 st 2020

Economic Evaluation of Beneficiating Nigerian Bentonite Using Periwinkle Shell and Mucuna Solannie

According to past studies, Nigerian Bentonites are found to be deficient in both fluid loss and rheological properties. Due to the deficiency of the Nigerian bentonite (NB), a good majority of bentonites used within Nigeria are imported. This research work seeks to evaluate the economic profitability of beneficiating the fluid loss and rheological properties of NB using periwinkle shell (PWS) and Mucuna Solannie (MS) as additives. The economic evaluation of this research seeks to point out the best possible action, based on available evidence. Two parameters—cost and outcome, are measured by the economic evaluation. From this measurement, an economic evaluation’s results will not exactly point out the better alternative, the way that an experimental trial would. If the most effective option from the evaluation is the cheapest, then it is the most cost effective option. In such a scenario, the most cost effective option is said to be the dominant alternative. From the economic evaluation of the PWS and MS additives performed during the course of this research, it can be said that these additives are economically profitable when added to local bentonite (LB), compared to the cost of using imported bentonite (IB) clay. Estimation of required equipment and facility for processing of additives (PWS and MS), calculation of discounted cash flow rate of return (DCF – ROR) for the investment and sensitivity analysis on the cash flow assumptions were carried out for the achievement of optimum results.

Formulation and characterization of water-based drilling fluids for gas hydrate reservoirs with efficient inhibition properties

Natural gas hydrates are presently considered as a potential source of future energy as it is widely distributed along the continental margins and in the permafrost areas. However, the drilling operation through such hydrate-bearing formation is quite risky because of unconsolidated formation, fragile nature of formation and uncontrolled dissociation of hydrate during drilling. In this study, an attempt was made to overcome the issues by a specially designed nanoparticle-enhanced water-based drilling fluid for its potential application in hydrate reservoirs. The rheological properties of different water-based drilling fluids, formulated by bentonite, carboxymethyl cellulose (CMC), SiO2 nanoparticle, barite and salts were studied both at high pressure and low temperature condition. Results show that the rheological properties, such as plastic viscosity, apparent viscosity, gel strength, yield point are highly promising. It has been found that silica nanoparticles and CMC reduce the fluid loss properties but CMC has a greater effect on fluid loss than silica nanoparticles. Zeta potential value of the formulated drilling fluids indicates their higher stability and strong function of the used nanoparticle. Inhibition effect of drilling fluid on hydrate formation was evaluated by using the drilling fluid with an optimized formulation in an autoclave hydrate cell at high pressure and low temperature. The experimental results reveal that the designed drilling fluid shows excellent inhibition effects on hydrate formation. This happens because of excellent thermodynamic and kinetic inhibition effects of CMC, salts and SiO2 nanoparticles.

Effect of Al2O3 nanoparticle on viscoelastic and filtration properties of a salt-polymer-based drilling fluid

ABSTRACT Conventional bentonite-based drilling fluids have associated problems while drilling troublesome or high-temperature zone due to degradation of rheological properties and excessive fluid loss. Clay particles present in the drilling fluid tend to block the pore throats and cause blockage to hydrocarbon flow. Similarly, polymers along with the filtrate loss, in the invaded zone, alter the wettability due to which there is a reduction in relative permeability to oil. All of these factors collectively cause a fall in production rates and demand stimulation jobs. The use of nondamaging drilling fluids, a particle-free salt-polymer-based drilling fluid, has addressed these problems by yielding a substantially less filtrate loss. However, at moderately high depths with high temperatures, this drilling fluid fails to maintain rheological properties and hence sagging, carrying, and fluid loss problems remerge. Sagging increases the equivalent circulation density which eventually decreases rate of penetration and induces formation damages. Hence, a need to further improve its properties is much required. This study has investigated the effect of aluminum oxide nanoparticles (Al2O3 NP) on these salt-polymer-based drilling fluids. A significant change was observed in rheological and fluid loss properties of drilling fluid (DF) when doped with different concentrations (0.5%, 0.8%, and 1%) of Al2O3 NP compared to the Base DF. Steady shear (rotational) tests were conducted to study the degree of shear thinning behavior of all the drilling fluids. It was observed that shear thinning behavior of the DF was increased with the addition of Al2O3 NP. Rotational measurements at 30°C showed a decrease in viscosity and shear stress of Al2O3 NP DF with an increase in concentration. However, at elevated temperatures of 60°C and 80°C, the reduction in viscosity of Al2O3 NP DF was substantially less than Base DF. One percent Al2O3 NP DF showed higher viscosity as compared to 0.5%, 0.8% Al2O3 NP, and Base DF at these conditions. To investigate the viscoelastic properties, oscillation tests were performed. Amplitude sweep tests showed an increase in storage modulus (G’) with an increase in Al2O3 NP concentration. While Base and 0.5% Al2O3 NP DF showed viscoelastic liquid in nature, 0.8% and 1% Al2O3 NP DF showed dominant storage properties indicating its viscoelastic solid nature at 30°C, 60°C, and 80°C. From the frequency sweep tests at higher temperatures, 0.8% and 1% Al2O3 NP DF, unlike Base and 0.5% Al2O3 NP DF, showed increase in complex viscosity at lower frequencies indicating structural build-up. Both rotational and thixotropic tests showed less structural regain time for 1% Al2O3 NP DF compared to other drilling fluid. Lastly, fluid loss control property of all the drilling fluids was investigated by measuring the filtrate loss volume in an API filter press apparatus. One percent Al2O3 NP DF showed a greater reduction in filtrate volume with Base DF showing the highest.

Improving the performance of oil based mud and water based mud in a high temperature hole using nanosilica nanoparticles

Oil-based mud (OBM), a non-Newtonian fluid, is known for its superior performance in drilling complex wells as well as combating potential drilling complications. However, the good performance may degrade under certain circumstances especially because of the impact of chemical instability at an elevated temperature. The same phenomenon occurs for water-based mud (WBM) when it is used in drilling under high temperature conditions. To prevent this degradation from occurring, numerous studies on utilizing nanoparticles to formulate smart fluids for drilling operations are being conducted worldwide. Hence, this study aims to evaluate the performance of nanosilica (NS) as a fluid loss reducer and a rheological property improver in both OBM and WBM systems at high temperature conditions. This study focuses on the impacts of different nanosilica concentrations, varying from 0.5 ppb to 1.5 ppb, and different mud weights of 9 ppg and 12 pg as well as different aging temperatures, ranging from ambient temperature to 300 °F, on the rheological performance of OBM and WBM. All the rheological properties are measured at ambient temperature, and additionally tests, including lubricity, electrical stability, and high-pressure high-temperature filtration measurements, are conducted, and rheological models are obtained. The performance of nanosilica is then studied by comparing each of the nanosilica-enhanced mud systems with the corresponding basic mud system, taking the fluid loss and rheological properties as the benchmark parameters. Nanosilica shows a positive impact on OBM and WBM, as the presence of nanosilica in the mud systems can effectively improve almost all their rheological properties.

Effect of surfactant chemistry on drilling mud performance

Drilling muds used in deepwater operations experience large variations in temperature, as well as pressure, when flowing through the different geometric conduits that are; the drill string, openhole (casing) - riser annuli present when drilling offshore. They behave as viscoelastic mixtures due to the suspension- and emulsion-dispersions used in their preparation. As a consequence, they display liquid-like and solid-like flow properties depending on the time scale of deformation they are subjected to. In addition to rate of deformation, environmental conditions such as temperature, and to a lesser extent pressure, are known to affect their rheological behavior.Nonionic surfactants are commonly used upstream in the stabilization of emulsions in drilling fluids, and in some instances as wetting agents. Inversion of pure emulsions systems stabilized by nonionic surfactants, from one type to another, as a result of temperature changes has been investigated and finds great application in the food and chemical industries.In this study, assessment of phase inversion occurrence in drilling muds, as well as resulting changes in their rheology was experimentally investigated at temperatures ranging from 0 to 90. Water- (WBM) and oil-based muds (OBM) samples were prepared using nonionic and ionic surfactants. Effect of surfactant nature and dispersed phase volume fraction on fluid loss properties of the different mud samples was equally carried at room temperature.Phase inversion of WBM samples stabilized by nonionic polyoxyethylene oleyl ether surfactants was observed for the range of conditions covered in the experimental investigation. Differences in flow behavior and apparent viscosity of the sample, as a result of inversion from one mud type to another, was equally noted.On one hand, the results underscored the importance of assessing potential application of nonionic surfactants to induce phase inversion in drilling fluids used for offshore operations. On the other hand, setbacks observed in the use of complex fluids for offshore drilling could possibly be accounted by the unknown occurrence of this phenomenon.

Synthesis and characterization of lignosulfonate/acrylamide graft copolymers and their application in environmentally friendly water- based drilling fluid

Acrylamide (AAm) was grafted onto lignosulfonate (LS) in the aqueous medium using two different H2O2/CaCl2 redox and potassium persulfate (KPS) thermal initiating systems at 30 and 55 °C, respectively. Resulting LS-g-PAAm graft copolymers were characterized by gravimetric, FT-IR and 1H NMR methods, from which initiator type and AAm concentration dependency of the AAm conversion (XAAm), grafting percentage (G(%)), grafting efficiency (GE) and copolymer structure were systematically evaluated. It was found that XAAm and G(%) can be affected significantly by the initiator type and AAm concentration while GE can mostly be affected only by the initiator type. Highest GE of 100% and grafting length of the PAAm chains onto LS was observed in the reaction LA-2 performed using redox initiator at 30 °C and initial weight ratio of AAm to LS of 20 while highest XAAm was observed in the reaction LA-3 performed using KPS initiator at 55 °C. Graft copolymers as well as LS with different amounts were used to prepare bentonite-based tap water (TWF), sea water (SWF) and NaCl salt saturated water (SSWF) fluids. Rheological and fluid loss (FL) properties of the above fluids were evaluated before and after hot rolling at 250 °F for 4 h. It was found that when an amount of 2.45–3.5 g/350 ml water is used; graft copolymers obtained from reactions LA-2 and LA-3 are able to improve rheological properties and to control FL and pH values in the TWF and SSWF, respectively, at low and high temperatures. All fluids showed shear thinning behavior with a gel-like structure under static conditions. Results revealed that thermal stability and salt resistance of the graft copolymers are high enough to be used as an effective additive in the high temperature and high salty water-based drilling fluids (WBDFs). An attempt was made to establish a relationship between the graft copolymer structure and its aqueous solution properties in the various water-based fluids. It was found that simultaneous higher GE (preferentially as high as 100%) and XAAm (as high as possible) in the graft polymers can results in a structure with the best performance in the WBDFs.