Mud System Research Articles

Formulation of a rice husk based non-damaging drilling fluid and its effect in shale formations

• The unconventional fluid such as non-damaging drilling fluid (NDDF) has formulated. • The NDDF of rice husk has shown improvement in the rheological properties. • The filtrate loss is reduced drastically in the presence of rice husk based NDDF. • Shale stability test of NDDF proves to be non-reactive with shale formations. • Study provide insights into the application of NDDF to produce unconventional liquid. Drilling a borehole is the most important process in the Petroleum Industry for crude oil or fossil fuel production. This facilitates via drilling fluid or mud for an efficient drilling operation to produce the crude oil. Conventional drilling fluid contains bentonite and barite which is a disadvantage for reservoir formations as these react with shale to cause extensive damage in the formation. Formation damage results in decreased productivity of the well thereby reducing its economic value and thus, this can be overcome by an unconventional fluid to produce the unconventional liquid. The unconventional liquid is crude oil or hydrocarbons which cannot be drilled or produced using the conventional method. Swelling and spalling also have big repercussion during drilling such as borehole collapse and stuck pipe using the conventional drilling fluid. In this work, counter these challenges, the unconventional fluid such as non-damaging drilling fluid (NDDF) of rice husk has formulated which is free of bentonite and barite. Rheological properties and shale stability test have investigated for the formulated NDDF. It is observed that the NDDF of rice husk has shown improvement in the rheological properties as compared to base mud. Also, the filtrate loss is reduced drastically in the presence of rice husk, which has the potential to minimize the formation damage and will be less reactive to the reservoir formations. NDDF is a polymer mud system free from clay or other materials which are used in the pay zone or production section and shale to minimize the formation damage. From the enhancing results of the shale stability test of rice husk based NDDF, this has prevented the swelling of the shale and highly helpful to enhance the wellbore stability which will be a potential advantage to the drilling operations of oil and gas industries.

Comparison of polymer-based slag-mud slurries used for drilling jobs of steam stimulated wells in the Lagunillas oilfield (Venezuela)

The mud-to-cement conversion or 'slag-mix' technology displays several advantages when compared to conventional well cementing operations. This alternative method means to combine drilling fluids, accelerators, and finely granulated slag as the hydraulic material. Steam injection is commonly used to improve crude oil production in the Lagunillas field (state of Zulia, NW Venezuela). This work compares the use of two slag-mix systems containing two polymer-based drilling muds during cementing of injection wells: an aqueous drilling fluid and an oil-in-water emulsion mud. After comparing the use of the two study drilling mud systems with a typical lignosulfonate slag-mix system, it can be stated that both systems may be suitable to be used in the application of the mentioned-above technology in steam stimulated wells. The aqueous formulations under study and a typical slag-mud slurry containing lignosulfonate show relatively similar values for most physic-mechanical properties. In contrast, the slag-mix emulsion system under consideration shows distinctive rheological and filtration behaviours compared to the other study polymer-based slag-mud slurry, but similar mechanical properties. [Received: April 26, 2019; Accepted: August 1, 2019]

Synergistic application of polypropylene and silica nanoparticle modified by (3-Aminopropyl) triethoxysilane for cuttings transport

Achieving the desired efficiency in cuttings transport has always been a challenge during drilling situations due to complex wellbore trajectories and drilling hydraulics. These issues require suitable additives to formulate the drilling muds. Hence, nanocomposite (NC) particles formed from silica and polypropylene was modified by (3-Aminopropyl) triethoxysilane (termed PP-SiO2 NC-NH2) and the impact of the concentrations of the PP-SiO2 NC-NH2 between 0.4 and 1.2 ppb on the cuttings transport efficiency (CTE) of complex water-based mud (WBM) system was assessed. Mud system containing 0.5 ppb PP-SiO2 NC-NH2 on CTE was measured and compared with that of partially hydrolyzed polyacrylamide (PHPA) using sandstone grains of diameters between 0.50 and 3.20 mm at hole angles 0, 30, 45, 60, and 90° with a 42 L/min pump rate. The zeta potential (ζ-potential), particle size distribution, morphology, and temperature resistance of the NC were examined. The ζ-potential data revealed the stability and the long-term stabilization of the modified NC in drilling muds. By adding the concentration of the modified NC into the WBM system, the thinning characteristics and consistency factors were enhanced as the NC concentration increases. Furthermore, the rheological test program reveals that the NC concentrations and 0.5 ppb PHPA increased the shear stress of the WBM with an increase in the shear rate. However, the mud system of PHPA exhibited a larger viscosity, while the NC samples showed a flat viscosity-profile. Also, the NC demonstrated better cuttings recovery than the PHPA product at 0.5 ppb concentration, especially at the worst hole angle of 45°. The cuttings recovery from a minimum to a maximum was found to occur in this order; 45°, 60°, 30°, 90°, and 0°. In contrast with the smallest and intermediate sand grains, the largest grains have complex and less fluid transport. With a pipe orbital motion of 150 rpm and a pump rate of 42 L/min, the CTE of the muds showed higher improvement. Overall, the mud properties of the modified NC exhibited a strong enhancing impact on the cuttings carrying capacity of the base mud than the PHPA.

Effect of high temperature ageing on TiO2 nanoparticles enhanced drilling fluids: A rheological and filtration study

Design of drilling fluids is critical to the techno-economic success of drilling a petroleum well bore and the present study is a forward step in that direction. Effect of TiO2 nanoparticles on the thermal stability of drilling fluid properties is evaluated using two different mud systems based on polyanionic cellulose (PAC) and hydroxyethyl cellulose (HEC). Drilling fluids were subjected to high temperature rolling conditions at 110 °C and 30 rpm for 16 hours in order to simulate the wellbore environment using a roller oven. Due to 16 h long hot rolling, the API FL values for DFB (base mud), DFP3 (1.0 w/v% PAC) and DFH3 (1.0 w/v% HEC) increased by ~56%, ~18% and ~46% respectively; whereas in presence of 0.5 w/v% nanoparticles respective figures were ~28%, ~16% and ~25%. In case of DFP3, AV at 25 °C was reduced due to hot rolling by ~34% without nanoparticles and by only ~15% in presence of nanoparticles. For DFH3, the percentage reduction in AV at 25 °C due to ageing was ~24% which decreased to ~16% for DFHN (1.0 w/v% HEC and 0.5 w/v% TiO2). It was found that nanoparticles imparted resistance to thermal degradation in rheological and filtration characteristics of drilling fluids. Filter cakes were studied using scanning electron microscopy and showed nanoparticles scattered over the surface of filter cakes which were filling the micro and nano sized gaps in the porous structure of mud cake and reducing the filtration rate. This study shows that using TiO2 nanoparticles along with a conventional fluid loss reducer additive not only enhances the efficacy of that additive but also improves the thermal stability and rheological properties of mud systems.

COMPARATIVE ANALYSIS OF CARBOXYMETHYL CELLULOSE AND PARTIALLY HYDROLYZED POLYACRYLAMIDE – LOW-SOLID NONDISPERSED DRILLING MUD WITH RESPECT TO PROPER-TY ENHANCEMENT AND SHALE INHIBITION

During drilling, different problems are encountered that can interfere with smooth drilling processes, including the accumulation of cuttings, reduced penetration rates, pipe sticking, loss of wellbore stability, and loss of circulation. These problems are generally encountered with conventional drilling mud, such as the bentonite–barite mud system. Formation damage is the most common problem encountered in bentonite mud systems with high solid content. In this work, we aimed to formulate two low-solid nondispersed (LSND) muds: carboxymethyl cellulose (CMC)–LSND mud and partially hydrolyzed polyacrylamide (PHPA)–LSND mud. A comparative analysis was performed to evaluate their property enhancements. LSND muds aid in maintaining hole stability and proper cutting removal. The results of this work show that the addition of both CMC and PHPA helps to improve drilling fluid properties; however, the PHPA–LSND mud was found to be superior. Shale swelling is a major concern in the petroleum industry, as it causes various other problems, such as pipe sticking, low penetration rates, and bit wear. The effect of these two LSND polymer muds in inhibiting shale swelling was analyzed using shale collected from the Champhai district of Mizoram, India.

Use of Low-ECD Synthetic-Based Mud During Topdrive Failure

While drilling in deepwater Gulf of Mexico, a topdrive failure forced the shutdown of all drilling operations for the rig operator and lasted for 114 hours (almost 5 days). At the time of the failure, the equivalent static density (ESD) was 11.36 ppg and the equivalent circulating density (ECD) was 11.5 ppg. The rate of penetration (ROP) was 100 ft/hr. Troubleshooting It was recommended that there be no utilization of the pumps while drilling was stopped, to reduce the chance of packing off the annulus with cuttings until the rotating and reciprocating could continue. During this time, a 100-psi backpressure was maintained using the managed-pressure drilling system. Kronos low-ECD synthetic-based mud (SBM) at a weight of 10.9 ppg was utilized during this event. During troubleshooting and repair work, a 1,500-bbl 11.4-ppg riser cap was spotted. Following the repair of the topdrive, a malfunctioning packer had to be replaced, causing additional delays. After the packer was set and the blowout preventers tested, the 11.4 ppg riser cap was displaced and subsequently replaced with 10.9-ppg low-ECD mud. The Kronos system was designed and maintained to have adequate suspension properties to maintain wellbore integrity without sag during unexpected downtime, even with cuttings left in the hole. The rig continued to trip into the hole to 9,800 ft. At that time, a bottom-up was circulated and a maximum of 575 units of gas was circulated out. Drilling then continued using a base oil and premix for dilution. The lost circulation material in the background continued to be blended into the dilution products being used at the time. During the drilling from 11,636 to 12,845 ft, the decision was made to increase the mud weight to 11.15 ppg. When the drilling continued from 12,845 to 13,234 ft, formation water was detected from the mud check entering the mud system. The system was treated to minimize the damage caused by formation water and maintain the properties sought by the operator. To assist in maintaining the desired weight and to prevent low-gravity solids from impacting the mud weight, two shakers were screened up to API Standard 120. At roughly the same time, the mud weight was increased to 11.2 ppg and then to 11.4 ppg. While continuing to drill, one of the engines that provided power to the mud pumps broke down, reducing the flow rate required to clean the hole. A cement unit was added to the pump to replace much of the volume lost with the broken mud pump. At 13,155 ft, the decision was made to call this current interval at total depth. The back-reaming process also started at that time. To assist with the hole cleaning, a high-viscosity sweep was blended and circulated. An additional high-viscosity sweep was blended and circulated, the second time at 9,058 ft. With continued back reaming through some tight spots to 7,272 ft, operators decided to wash back down 7,938 ft and pump one more high-viscosity sweep. Once the hole was clean, a flow check was performed and operators began to pull out of the hole.

Influence of (3–Aminopropyl) triethoxysilane on entrapped polypropylene at nanosilica composite for shale swelling and hydration inhibition

The unforgiving shale formations require special shale inhibitors to mitigate wellbore instability problems. (3–Aminopropyl) triethoxysilane polypropylene-nanosilica composite (PNSC + NH2) was evaluated in water-based drilling muds (WBDMs) as a clay swelling and hydration inhibitor. The size distribution, functional groups, morphology, and thermal stability of the PNSC + NH2 were studied. Rheological and filtrate volume tests were carried out to determine the influence of the PNSC + NH2 on WBDMs. The clay swelling inhibition performance of the PNSC + NH2 mud system was examined and compared with that of potassium chloride (KCl) and KCl + partially hydrolyzed polyacrylamide (KCl + HPAM) through clay swelling inhibition test, extended clay swelling inhibition test (inhibition longevity test), and BET analysis test. Four shale specimens were prepared with compactor cell for the measurement of clay swelling using the Linear Swell Meter. Drilling muds were examined on 16 mm thick-compacted shale pellets using the highest concentration of smectite. A shale rolling recovery test was conducted to determine the shale hydration-retardation. Results showed that the PNSC + NH2 particle has good dispersibility, with a size distribution predominantly distributed between 80 and 390 nm. The inclusion of 1.5w/v% PNSC + NH2 concentration enhanced the plastic viscosity and yield point of WBDM from 11 to 15 mPa s and 9–14 Pa, respectively. Also, it reduced the API filtrate volume of the WBDM from 10.2 to 7.8 ml. The clay swelling inhibition performance of the WBDM for 36 h showed 62% swelling and was reduced to 42% by KCl, 33% by KCl + HPAM, and 28% by PNSC + NH2. When the inhibition test was extended to 60 h, the swelling increased to 44% for KCl, 40% for KCl + HPAM, and 29% for PNSC + NH2 mud systems. These results revealed that the PNSC + NH2 has the best inhibition performance due to its ability to provide the greatest long-lasting inhibiting effect on the clay surface. When the shale cuttings with the various mud systems were subjected to 150 °C for 16 h in an ageing steel cell, the shale recovery rate at 1.5w/v% concentration confirmed that the PNSC + NH2 exhibited 75.3 wt%, while that of the base mud, KCl, and KCl + HPAM systems demonstrated 33.6, 58.4, and 63.1 wt%, respectively. The BET surface area of the shale reduced significantly by 52.3% with 1.5w/v% PNSC + NH2 from 14.72 to 7.02 m2/g. The wettability determination of the shale surface showed a contact angle of 36.8° which improved to 68.4° by 81.0% with 2.0w/v% PNSC + NH2 concentration. The application of PNSC + NH2 for clay swelling and hydration inhibition proved to be promising and could be effective for drilling shales.

Methane hydrate phase behaviour in EMIM-Cl water based mud (WBM): An experimental and modelling study

Gas hydrate sediments are known as future energy source and potential technique for the storage CO2. However, the drilling of hydrate sediments are challenged with inappropriate drilling mud systems. Ionic liquids are introduced as novel drilling mud agents that can enhance the rheology of water-based mud and at the same time manage hydrate formation risk during hydrate sediments drilling. However, the disturbances of ionic liquid water-based mud filtrate on hydrate in-situ rocks is not well understood. To achieve this, the phase behaviour of methane hydrates in 1-Ethyl-3-methy-limidazolium chloride (EMIM-Cl) water-based mud at different EMIM-Cl concentrations were measured using the isochoric T-cycle technique in a high-pressure hydrate cell within the temperatures and pressures and ranges from 273.68 – 286.10 K and 3.60 – 9.70 MPa, respectively. The rheological properties of the EMIM-Cl mud systems were tested using a TA rheometer at 271.15 K – 313.15 K. The presence of EMIM-Cl had very minimal disturbances (less than 0.5 K shift) on methane hydrate at the studied concentrations. The disturbance of EMIM-Cl of methane hydrates in pure water system is reduced by 74% in drilling mud systems. The use of EMIM-Cl at 3 wt.% could reduce the methane hydrate disturbance effect 2 times as methanol. EMIM-Cl reduced the thermal degradation of the mud by 55% at 1 wt.% with very low viscosity. The viscosity reduction of the mud occurs at lower EMIM-Cl concentrations. Suggesting that, using ionic liquids water-based mud to drill hydrate sediments will reduce the risk of releasing compacted methane gas into the borehole while drilling. In addition, an attempt is made to predict the methane hydrate equilibrium curve in the presence of the EMIM-Cl using the Dickens and Quinby-Hunt, (1997) model.

The Effect of Nano Materials on Lost Circulation Control of Azkand Formation in Khabaz Oil Field

Experimental tests were carried to control lost circulation in the Khabaz oil field using different types of LCMs including Nano-materials. A closed-loop circulation system was built to simulate the process of lost circulation into formations. Two dolomite plugs were used from different depths of the formation of Azkand in Khabaz oil field. The experimentations were carried out to study the effect of different types of LCMs, cross-linked copolymer (FLOSORB CE 300 S), SiO2 NP, and Fe2O3 NP, on mud volume losses as a function of time.
 The rheological measurements of the nanoparticles-reference mud system showed that both of the SiO2 NP and Fe2O3 NP worked best at 1.2 g/l. and the closed-loop circulation system showed that SiO2 NP cured losses by 48.3% and 37.5% for core plugs 5C1 and 1C2 respectively which is better than Fe2O3 NP loss curing which was 37.9% and 31.3% for core plugs 5C1 and 1C2 respectively.
 On the other hand, FLOSORB CE 300 S- Fe2O3 NP-reference mud systems cured losses up to 69% with 0.25g/l FLOSORB CE 300 S and 79.3% with 0.5 g/l FLOSORB CE 300 S which is better than the FLOSORB CE 300 S- SiO2 NP-reference mud systems results.

Well Factory Practice in Bailu Lake Cluster Wells

It is very difficult to economically develop Bailu Lake low permeability reservoir, facing severe anti-collision challenge, as well as trajectory controlling and cuttings carrying of high difficulty, beyond that the reservoir located in the scenic area, where the well site area was limited and the environmental protection requirements were very strict. On the basis of learning the foreign companies’ successful experience on cluster well factory, the authors analyzed the situation and difficulties of Bailu Lake well factory project initially, thus proposing Bailu Lake well factory overall optimized scheme, including slot drilling sequence and trajectory optimization. Through fast rig moving technique, PDC bit and motor optimization and high inhibitive and environment friendly CaCl2 mud system, the rig moving time was shorten by 2 days averagely and one run safe drilling in the second spud. Finally, the total 43 wells were successfully completed, and the average well drilling cycle was shorten by 15.49 days, which had achieved good effects.

Soil chemical properties following a one‐time spent drilling mud application on native prairie

AbstractLandspraying while drilling (LWD) is an approved disposal method for water‐based drilling mud (WBM) systems in western Canada, where the mud is applied either on arable or vegetated land. This study examined the effects of a single LWD application (0, 15, 20, 40, or 80 m3 ha−1) on native prairie soil properties. Results from the study showed a significant increase in Na concentration and sodium adsorption ratio (SAR) in the 0‐ to 7.5‐cm depth. However, the highest SAR attained (3.46) after application at the 80 m3 ha−1 rate remained below levels considered detrimental to soil structure. Electrical conductivity (EC) also increased with the LWD rate but peaked at levels (447 μS cm−1 in the 0‐ to 2.5‐cm depth) much lower than the threshold for most plant species, and the effects on EC had disappeared by the end of the first year of mud application. Available P concentration (modified Kelowna method), averaged across sampling times and the two depths (0‐ to 2.5‐ and 2.5‐ to 7.5‐cm), increased from 7.4 to 11 mg kg−1 as LWD rate increased from 0 to 80 m3 ha−1. Although the available P remained at concentrations suboptimum for most crops, such concentrations may impact native prairie vegetation adapted to very low P. Drilling mud applications generally had no significant effect on available N. The application of WBM systems on the native prairie at recommended rates in western Canada may not be detrimental to soil quality and plant growth in this ecosystem.

Development of a highly automated mobile rig for the Australian CSG market

In Q2 2020, a fully automated rig will enter the coal seam gas fields of Queensland, to work for a major operator. It is expected to be 20–30% faster than current operations. This document describes the upfront iterative design process with local potential users. Following discussions with various contractors and operators it became evident that there was a gap to bridge between operator and contractor targets and in what current operations have to offer. Both strive for the highest safety levels and operational efficiency, reducing the overall time per well, completed by minimising environmental impact. The above fits in the overall industry trend of transformation from mechanised rigs towards fully automated hands-free operated rigs. It was with these ingredients that the basis of a new iterative design process was formed, in which input from the operator field lieutenants, contractor rig crews and the supporting office was translated into a technical design. The target was set to reduce 20–30% of time per well. Key elements were the choice for road legal trailerised loads with no loose items, which resulted in rig moves of 4–6 h. Fully automated sequenced pipe tripping and casing running contributed to big improvements in efficiency and safety level (no people on the floor during standard operations). Performance can be real-time evaluated and optimised by collecting all rig and downhole data on the OPC server. The server also controls the mud system, downhole data and other important systems. This enables through-life time optimisation.

Hydrate‐filled Fracture Formation at Keathley Canyon 151, Gulf of Mexico, and Implications for Non‐vent Sites

AbstractNear‐vertical hydrate‐filled fractures are found in subseafloor marine muds, at both advective methane vent sites and at sites without obvious methane and fluid advection (non‐vent sites). At non‐vent sites, the mechanisms that transport methane to the fractures and control how hydrate‐filled fractures form are not well understood. However, these mechanisms are important to establish, as most of Earth's natural gas hydrate is likely bound in marine mud systems. Herein, we focus on understanding the origin of hydrate and how fracture form at non‐vent sites by examining previously hydrate‐bearing fractures in conventional cores taken from Keathley Canyon 151, U.S. northern Gulf of Mexico, drilled by the Gas Hydrate Joint Industry Project in 2005. We combine information from well logs, sediment cores, and science party results and add new X‐ray computed tomography of archival sections and scanning electron microcopy of core samples to develop a conceptual model. We propose that locally generated microbial methane is transported via diffusion from small pores in marine mud into biomineralized burrows with larger pore size in a process called short‐range migration. Hydrate forms in burrows once the methane diffuses into them and the dissolved methane concentration exceeds the solubility threshold. When hydrate fills a burrow, heave from additional hydrate growth places stress on the burrow edges, expands the fracture, and creates additional void space in which methane can diffuse and continue forming hydrate. Fractures slowly propagate in the direction of maximum principal stress.

A novel oil-in-water drilling mud formulated with extracts from Indian mango seed oil

Drilling muds with less environmental impact are highly desired over conventional diesel-based mud systems, especially in light of the emerging strict environmental laws. In this article, a novel oil-in-water (O/W) emulsion drilling fluid formulated with a methyl ester extracted from Indian mango seed oil was evaluated. The effect of the weight percent of different constituents of the emulsion/suspension including the oil phase, bentonite, and polyanionic cellulose polymer on the rheology and the fluid loss was examined. The methyl ester oil phase/mud system displayed superior physical, chemical, rheological and filtration properties relative to the diesel and the mango seed oil. Eco-toxicity of the methyl ester and diesel (O/W) emulsion mud systems was assessed using the acute lethal concentration test. The Indian mango methyl ester (O/W) emulsion mud displayed much less impact on fish population. Flow characteristics collected from the flow model at 85 °C suggested excellent shear thinning behavior of the Indian mango methyl ester (IMME) (O/W) emulsion mud. Moreover, the IMME (O/W) emulsion displayed strong pseudoplastic behavior, an attractive feature in a drilling mud, with increasing clay content and polymer concentration. The methyl ester mud was thermally stable over a wide range of the constituent concentrations. Furthermore, a particle size analysis revealed that engineered drilling muds targeting suspension of particles with certain size range can be formulated by changing the volume fraction of the methyl ester in the mud system.

Experimental and modelling of the impact of quaternary ammonium salts/ionic liquid on the rheological and hydrate inhibition properties of xanthan gum water-based muds for drilling gas hydrate-bearing rocks

In this study, quaternary ammonium salts (QAS) and ionic liquid (IL) were used as additives in xanthan gum water-based muds formulations to investigate their rheological and hydrate inhibitive potentials in drilling gas hydrate sediment. The QAS/IL used were TMABr, TPrABr, TMACl, and EMIMCl. The mud rheological characterisation was performed at a controlled shear rate of 1 s−1 to 200 s−1 at -2 °C–40 °C. The hydrate test was conducted in a high-pressure reactor at 8 MPa and -2 °C. The hydrate nucleation onset time was predicted using the classical nucleation theory (CNT) model. The rheology and hydrate results confirmed the potential application of QAS/IL in drilling mud formulations for drilling hydrate sediments. The presence of QAS/IL in the base mud suitably reduced the mud viscosity and yield stress, which are desired properties for generating turbulent flow to enhance cuttings transport, especially in high angle wellbores. The rheological properties of water-based mud were found to be significantly controlled or affected by the cation, anion, and alkyl chain length type of QAS/IL. However, the anion effect is more dominant and exhibit a critical concentration depending on its respective ionic strength. Further FTIR analysis confirmed the presence of N–O stretching which supports the performance of TMA+ over EMIM+ to reduce the mud yield stress. In addition, the thermal degradation of the base mud was significantly reduced in the presence of QAS/IL. Amongst the studied additives, TMACl and TPrABr WBMs completely prevented hydrate plugs in the mud system. Furthermore, the CNT model accurately predicted the hydrate onset time with APE <2%. The QAS/IL in the WBM systems exhibited minimal to negligible disturbance (<0.5 K shift) on the methane hydrate phase boundary compared with commercial hydrate additives at 3 wt%. This study provides guidelines to design efficient QAS/IL WBMs for drilling gas hydrate rocks.

NORM, a Health concern to Personnel exposed to Formation Drill Cuttings – Regulation issue in Nigeria

During the drilling operations, formation rocks or shales drilled are removed from the wellbore as drill cuttings. These cuttings are real-time representative of the formation being drilled at that section of the wellbore, and it represents the formation of compositions and properties. Regulations for most oil well developments stipulate that the methods used for managing drill cuttings are dependent on the nature and type of drilling mud system used for the drilling operation. When the formation with these relatively high NORM contents is drilled using the drilling mud, these NORM traces are transported to the surface as drill cuttings; thus, exposing the personnel to health dangers and the immediate environment. The short and long-term health effects of NORM exposure include skin burns, harmful tissues reactions, increase the risk of lung cancer, mutation of somatic cells and leukemia. DPR has some standards and guidelines established to effectively police and regulate E&P industry activities in Nigeria. These guidelines and standards also take into consideration, the need for advanced pollution control strategies and technological treatments. However, the presence and harmful consequences of NORM in these drill cuttings are not considered in the current form of these regulations and guidelines. This study proposes the inclusion of NORM as a means of updating the already established guidelines and regulations for handling and treating these drill cuttings because they constitute the majority of the waste and toxic materials generated during drilling operations.

Assessing the impact of an ionic liquid on NaCl/KCl/polymer water-based mud (WBM) for drilling gas hydrate-bearing sediments

Herein, 1-methyl-3-octylimidazolium tetrafluoroborate (OMIM-BF4) was tested as a potential additive to enhance the rheological and hydrate inhibition properties of polymer water-based muds (WBMs) for drilling natural gas hydrate sediments. API standards were adopted for the mud testing with and without OMIM-BF4, while the hydrate study was conducted using a high-pressure reactor at 8 MPa and −2 °C. The presence of OMIM-BF4 efficiently improved the rheological properties of the PAC and XGUM based muds by decreasing their flow behavior index by 4.97% and 47.77% and increasing their consistency index by 96.00% and 33.63%, respectively. The XGUM based mud system exhibited efficient rheological properties suitable for drilling hydrate reservoir compared with the PAC based mud system with and without OMIM-BF4. The Hershel-Bulkley model best predicted the rheological properties of all the mud systems by exhibiting less Mean Percentage Error (MPE) values in the range of 1.39% – 24.71%. Furthermore, the presence of OMIM-BF4 greatly inhibited methane hydrate formation in both PAC and XGUM water-based mud systems due to its kinetic inhibition efficiency mainly arising from its long alkyl chain hydrophobic adsorption activity on the hydrate crystals.

Determining the optimum concentration of multiwalled carbon nanotubes as filtrate loss additive in field-applicable mud systems

In a bid to combat fluid loss in muds where the effects of high downhole temperatures have pronounced effects on conventional fluid loss additives, several materials have over time been evaluated. One of such materials is the multiwalled carbon nanotubes (MWCNTs). Most studies in the literature limit the scope of their investigation to how the MWCNT affects mud rheology when added in minute concentrations (0.01–1 ppb). In this study, however, the performance of high concentrations (0.5–3 ppb) of multiwall carbon nanotubes as fluid loss control additives in field-applicable mud systems was put to the test. The essence was to establish an optimal concentration useful for field applications. The degree to which the introduction of varying concentrations of the MWCNT altered the muds capacity to control filter loss was the cardinal areas evaluated. The following are the major outcomes of the experimental study: The plastic viscosity, the yield point and the gel strengths showed a progressive increase as the concentration of the MWCNT in the mud increased for both the water- and oil-based muds. However, an optimum concentration of 2 ppb was observed for the water-based mud. For the filter loss tests on the oil-based mud, the results indicate that low concentrations (0.5 ppb) of the MWCNT led to high filter loss volumes (15 ml), but an increase up to 2.5 ppb reduced the margin of the filter loss volume by 52% (7 ml) from the initial value and a 50% decrease for the standard case. In the case of the water-based mud, equivalent amounts of MWCNT recorded less fluid loss than the standard. A moderately hard and firm cake was reported for all concentrations of the standard and MWCNT for the water- and oil-based muds; however, their cake thickness values were 2 mm and 1 mm for the water- and the oil-based muds, respectively.

The effect of salts and haematite on carboxymethyl cellulose\u2013bentonite and partially hydrolyzed polyacrylamide\u2013bentonite muds for an effective drilling in shale formations

A common issue encountered by drilling engineers during drilling operation in oil and gas industries is that simple water-based muds are not suitable for deeper depth and certain clay-swelling formations. Another option as to increasing the density of the drilling mud which brings about an increase in filtration loss, additives may be added to improve the fluid properties. This paper aims on determining the effectiveness of common salts, sodium chloride (NaCl) and potassium chloride (KCl), and haematite on the rheological properties of optimized carboxymethyl cellulose (CMC)–bentonite and partially hydrolyzed polyacrylamide (PHPA)–bentonite muds. Both CMC and PHPA polymer act as fluid loss-reducing agents and viscosifiers for normal bentonite water-based mud. The mud is further enhanced to counter certain swelling formations such as shale through the addition of NaCl and KCl. These salts inhibit the shale formation from swelling through its ions by entering the lattice of the drilling mud or formation instead of the water ions. Haematite, on the other hand, basically functions to increase mud density and acts as a substitute for barite. The effect of haematite on drilling fluid was studied because it gives higher degree of rheological parameters and increases density as compared to barite. So, an optimized concentration of additives was determined for both CMC–bentonite and PHPA–bentonite mud systems, respectively. Three grams of KCl and 3 g haematite were used for CMC–bentonite mud, while 3 g KCl and 1 g haematite were added into PHPA–bentonite mud. Both these muds have shown swelling reduction as compared to those without the use of additives. Moreover, they exhibited Herschel–Bulkley fluid behaviour according to the power law model where their ‘n’ value was less than 1, while their yield points were more than zero. Since shale sloughing is a major problem faced during drilling operation, it leads to major complications in drilling. So, finally, both the formulated drilling fluids are tested to analyse their effect in shale formations by static immersion test. The shale rock was collected from Champhai District of Mizoram. Both the formulated muds exhibited great results as swelling in shale rock was reduced for both muds and optimum rheological values were maintained.

Improving the Lifting Capacity of Drilled Cuttings Using Henna Leaf Extracts and Lignite in Bentonite Water-based Drilling Mud

One of the basic functions of drilling fluids is to transport drilled cuttings to the surface. Bentonite with low solids content is preferred in carrying out this task. However, a low amount of bentonite in the drilling mud is incapable of effective cuttings lifting and suspension. In this study, a new, green, low-cost henna leaf extract and lignite in bentonite water-based drilling mud was used to transport cuttings to the surface. The effects of three hole angles (0°, 45° and 90°) were examined at different cuttings size diameters (0.5 mm, 1.0 mm, 2.0 mm and 2.4 mm) for the mud systems. The average cuttings transport efficiencies were found to be in the following order: 52-94% for 0.5 mm diameter, 45-93% for 1.0 mm diameter, 38-90% for 2.0 mm diameter, and 33-83% for 2.4 mm diameter. Viscosity and hole angle are directly related to cuttings transport efficiency. A plastic viscosity of 16 cP and yield point of 12.5 lb/100ft² were the most effective mud properties for a 45° hole angle, which needs attention while preparing the drilling mud. Addition of henna and lignite can be used to improve the rheological and filtration properties of bentonite water-based drilling mud.