Improving the anti-collapse performance of water-based drilling fluids of Xinjiang Oilfield using hydrophobically modified silica nanoparticles with cationic surfactants

Wellbore instability,especially drilling with water-based drilling fluids(WBDFs)in complex shale for-mations,is a critical challenge for oil and gas development.The purpose of this paper is to study the feasibility of using hydrophobically modified silica nanoparticle(HMN)to enhance the comprehensive performance of WBDFs in the Xinjiang Oilfield,especially the anti-collapse performance.The effect of HMN on the overall performance of WBDFs in the Xinjiang Oilfield,including inhibition,plugging,lu-bricity,rheology,and filtration loss,was studied with a series of experiments.The mechanism of HMN action was studied by analyzing the changes of shale surface structure and chemical groups,wettability,and capillary force.The experimental results showed that HMN could improve the performance of WBDFs in the Xinjiang Oilfeld to inhibit the hydration swelling and dispersion of shale.The plugging and lubrication performance of the WBDFs in the Xinjiang Oilfield were also enhanced with HMN based on the experimental results.HMN had less impact on the rheological and filtration performance of the WBDFs in the Xinjiang Oilfield.In addition,HMN significantly prevented the decrease of shale strength.The potential mechanism of HMN was as follows.The chemical composition and structure of the shale surface were altered due to the adsorption of HMN driven by electrostatic attraction.Changes of the shale surface resulted in significant wettability transition.The capillary force of the shale was converted from a driving force of water into the interior to a resistance.In summary,hydrophobic nanoparticles presented afavorable application potential for WBDFs.

The Conversion of Non-Dispersed Polymers into Low-Potassium Anti-Collapse Drilling Fluids

Different drillingfluid systems are designed according to mineral composition,lithology and wellbore stability of different strata.In the present study,the conversion of a non-dispersed polymer drillingfluid into a low potas-sium anti-collapsing drillingfluid is investigated.Since the two drillingfluids belong to completely different types,the key to this conversion is represented by new inhibitors,dispersants and water-loss agents by which a non-dispersed drillingfluid can be turned into a dispersed drillingfluid while ensuring wellbore stability and reason-able rheology(carrying sand—inhibiting cuttings dispersion).In particular,the(QYZ-1)inhibitors and(FSJSS-2)dispersants are used.The former can inhibit the hydration expansion capacity of clay,reduce the dynamic shear force and weaken the viscosity;the latter can improve the sealing effect and reduce thefiltrate loss.The results have shown that after adding a reasonable proportion of these substances(QYZ-1:FSJSS-2)to the non-dispersed polymer drillingfluid,while the apparent viscosity,plastic viscosity,structural viscosity andfluidity index under-went almost negligible changes,the dynamic plastic ratio increased,and thefiltration loss decreased significantly,thereby indicating good compatibility.According to the tests(conducted in the Leijia area),the density was 1.293 g/cm3,and after standing for 24 h,the SF(static settlement factor)was 0.51.Moreover,thefiltration loss was reduced to 4.0 mL,the rolling recovery rate reached 96.92%,with excellent plugging and anti-collapse performances.

Hydrophobic Small-Molecule Polymers as High-Temperature-Resistant Inhibitors in Water-Based Drilling Fluids

Water-based drilling fluids can cause hydration of the wellbore rocks,thereby leading to instability.This study aimed to synthesize a hydrophobic small-molecule polymer(HLMP)as an inhibitor to suppress mud shale hydration.An infrared spectral method and a thermogravimetric technique were used to characterize the chemical composition of the HLMP and evaluate its heat stability.Experiments were conducted to measure the linear swelling,rolling recovery rate,and bentonite inhibition rate and evaluate accordingly the inhibition performance of the HLMP.Moreover,the HLMP was characterized through measurements of the zeta potential,particle size distribution,contact angles,and interlayer space testing.As confirmed by the results,the HLMP could successfully be synthesized with a favorable heat stability.Furthermore,favorable results were found for the inhibitory processes of the HLMP on swelling and dispersed hydration during mud shale hydration.The positively charged HLMP could be electrically neutralized with clay particles,thereby inhibiting diffusion in the double electron clay layers.The hydrophobic group in the HLMP molecular structure resulted in the formation of a hydrophobic membrane on the rock surface,enhancing the hydrophobicity of the rock.In addition,the small molecules of the HLMP could plug the spaces between the layers of bentonite crystals,thereby reducing the entry of water molecules and inhibiting shale hydration.

Optimization of Anti-Collapse Drilling Fluid Systems with High Potassium Content

The ash mudstone in some oil formations is highly water-sensitive.The oil formation is fractured,and the risk of well leakage and collapse is not negligible.This study presents a countermeasure for well collapse prevention,based on a“force-chemistry synergistic balance”approach and the utilization of environmentally friendly and efficient hydration inhibitors.The relevance of this approach is demonstrated considering a drilling fluid system with the high potassium content.The analysis shows that the system can maintain good rheological properties,filtration loss and suspension stability even after aging at 130℃ for 16 h.The primary roll recovery of rock chips is better than 98%.The secondary rolling recovery rate is 89%.The rapid water loss is close to zero.The effects of carrying rock,sand,hydration inhibition and dispersion of drill chips are all noticeable.

Study on a Polyamine-Based Anti-Collapse Drilling Fluid System

In complex strata, oil-based drilling fluid is the preferred drilling fluid system, but its preparation cost is high, and there are hidden safety risks. Therefore, the new progress of high-performance anti-collapse water-based drilling fluid at home and abroad is analyzed. It is difficult to prevent and control the well collapse. Once the well wall instability problem occurs, it will often bring huge economic losses to the enterprises, and the underground safety accidents will occur. In order to ensure the stability of the well wall and improve the downhole safety, the key treatment agent of water-based collapse drilling fluid is selected, the anti-collapse drilling fluid system is formulated, the evaluation method of drilling fluid prevention performance is established, and a set of water-based drilling fluid system suitable for easy to collapse strata in China is selected to ensure the downhole safety. The development trend of high performance anti-collapse water-based drilling fluid is expected to provide a reference for the research of high performance anti-collapse water-based drilling fluid system and key treatment agent.

High temperature and high pressure rheological properties of high-density water-based drilling fluids for deep wells

To maintain tight control over rheological properties of high-density water-based drilling fluids, it is essential to understand the factors influencing the theology of water-based drilling fluids. This paper examines temperature effects on the rheological properties of two types of high-density water-based drilling fluids （fresh water-based and brine-based） under high temperature and high pressure （HTHP） with a Fann 50SL rheometer. On the basis of the water-based drilling fluid systems formulated in laboratory, this paper mainly describes the influences of different types and concentration of clay, the content of a colloid stabilizer named GHJ-1 and fluid density on the rheological parameters such as viscosity and shear stress. In addition, the effects of aging temperature and aging time of the drilling fluid on these parameters were also examined. Clay content and proportions for different densities of brine-based fluids were recommended to effectively regulate the rheological properties. Four theological models, the Bingham, power law, Casson and H-B models, were employed to fit the rheological parameters. It turns out that the H-B model was the best one to describe the rheological properties of the high-density drilling fluid under HTHP conditions and power law model produced the worst fit. In addition, a new mathematical model that describes the apparent viscosity as a function of temperature and pressure was established and has been applied on site.

Carbon nanotube enhanced water-based drilling fluid for high temperature and high salinity deep resource development

Drilling fluids face failure during drilling deep reservoir with high temperature and high salt.The experimental results show that high temperature and salinity reduce the negative charge on the surface of bentonite in the drilling fluid and cause the coalescence of bentonite particles.As a result,the particles coalesce,the grid structure is destroyed,and the rheological properties,rock-carrying capacity and filtration properties are lost.To resolve the foregoing,in this study,0.05-wt%carbon nanotubes are introduced into a 4%bentonite drilling fluid under conditions where the temperature and concentration of added Na Cl reach 180°C and 10 wt%,respectively.The carbon nanotubes adsorb on the bentonite surface and increase the space among bentonite particles.The steric hindrance prevents the coalescence of bentonite in high temperature and high salt environment.Thus bentonite maintains the small size distribution of bentonite and supports the bentonite grid structure in the drilling fluid.As a result,the rock-carrying capacity of the drilling fluid increases by 85.1%.Moreover,the mud cake formed by the accumulation of small-sized bentonite particles is dense;consequently,the filtration of bentonite drilling fluid reduced by 30.2%.

Notoginsenoside as an environmentally friendly shale inhibitor in water-based drilling fluid

The demand for non-toxic and biodegradable shale inhibitors is growing in the drilling industry.In this paper,the effect of notoginsenoside(NS)as a new,environmentally friendly inhibitor of shale hydration is systematically studied for the first time.The inhibition performance of NS was evaluated via inhibition evaluation tests,including mud ball immersion tests,linear expansion tests,shale rolling recovery tests,and compressive strength tests.The inhibition mechanism of NS was analyzed using Fourier transform infrared spectroscopy(FTIR),contact angle measurements,particle size distribution determination,thermogravimetric analysis(TGA),and scanning electron microscopy(SEM).The experimental results demonstrate that NS is able to adhere to the clay surface,forming a hydrophobic film that prevents the entry of water molecules and inhibiting the hydration dispersion of the clay.Because of this,NS can maintain the original state of bentonite pellets in water,which can effectively reduce the swelling rate of bentonite,increase the recovery rate of shale drill cuttings,maintain the strength of the shale,and therefore maintain the stability of the borehole wall during drilling.In addition,NS is non-toxic,degradable,and compatible with water-based drilling fluids.The above advantages make NS a promising candidate for use as an environmentally friendly shale inhibitor.

A new environmentally friendly water-based drilling fluids with laponite nanoparticles and polysaccharide/polypeptide derivatives

Considering the increasing environmental pressure,environmentally friendly and high-performance water-based drilling fluids(WBDFs)have been widely studied in recent years to replace the commonly used oil-based drilling fluids(OBDFs).However,few of these drilling fluids are entirely composed of natural materials,which makes it difficult to achieve real environmental protection.Using laponite nanoparticles and various derivatives of natu ral mate rials,including cro sslinked starch,cellulose composite,gelatin ammonium salt,poly-l-arginine,and polyanionic cellulose,a kind of environmentally friendly water-based drilling fluid(EF-WBDF)was built for drilling in environment-sensitive areas.The properties of this EF-WBDF were evaluated by thermal stability tests on rheology,filtration,inhibition,and salt contamination.Besides,biological toxicity,biodegradability,heavy mental content and wheat cultivation tests were conducted to investigate the environmental factor of EF-WBDF.Results showed that EF-WBDF displayed satisfactory thermal resistance up to 150℃,and the rheological properties did not suffer significant fluctuation,showing potential application in high-temperature wells.The optimal rheological model of EF-WBDF was Herschel-Bulkley model.This EF-WBDF performed an eligible filtration of 14.2 mL at 150℃and a differential pressure of 3.5 MPa.This fluid could still maintain colloidal stability after being contaminated by 7.5%NaCl or 0.5%CaC1_(2).Meanwhile,rather low clay swelling degree of 2.44 mm and high shale recovery of more than 95%ensured the inhibitive capability of EF-WBDF.Furthermore,EF-WBDF presented a half maximal effective concentration(EC_(50))of51200 mg/L and a BOD/COD ratio of 47.55%,suggesting that EF-WBDF was non-toxic and easily biodegradable.The wheat cultivated in EF-WBDF could grow healthily,beneficial for reducing the adverse impact on ecological environment.The formed EF-WBDF has a promising future for drilling in environment-sensitive and high-temperature areas.

Investigation of regulating rheological properties of water-based drilling fluids by ultrasound

Regulating rheological properties of water-based drilling fluids has always been a hot topic.This paper proposed a new method for regulating rheological properties of water-based drilling fluids by ultrasonic field.The experimental results showed that the ultrasound increased the viscosity and yield point of bentonite suspension by reducing the particle size of clay,destroying the network structure between clay particles,increasing the mud yield and the cation exchange capacity of bentonite,and promoting the hydration dispersion of bentonite.The change of rheological property showed a memory effect at room temperature and high temperature.Besides,the ultrasonic energy affected the network structure between clays and polymer chains,thus regulating the rheological properties of the bentonite-polymer system.For two types of drilling fluids investigated,the rheology of the poly-sulfonate drilling fluid was regulated by damaging the grid structure between additives and clays by low-power ultrasound and reducing the clay particle size by high-power ultrasound,while the rheology of the deep-water drilling fluid was mainly regulated by disentangling the spatial grid structure between additives.Additionally,ultrasound showed no effect on the lubricity,inhibition and stability of drilling fluids,which proved the feasibility of ultrasound to regulate rheological properties of water-based drilling fluids.

Application of sustainable basil seed as an eco-friendly multifunctional additive for water-based drilling fluids

Basil seed,containing anionic heteropolysaccharides in its outer pericarp,swells as gelatinous hydrocolloid when soaked in water.In this study,basil seed powder(BSP)was used as a multifunctional additive for water-based drilling fluids.The chemical composition,water absorbency,rheological properties of aqueous suspension of BSP were tested.The effect of BSP on the rheological and filtration of bentonitebased drilling fluid before and after thermal aging was investigated.The inhibition characteristics were evaluated by linear swelling,shale cuttings dispersion and shale immersion test.Lubricity improvement by BSP was measured with extreme pressure lubricity test.The results revealed that incorporation of BSP into bentonite suspension improved rheological and filtration properties effectively after thermal aging of 120℃.BSP exhibited superior inhibitive capacity to xanthan and synergistic effect with KCl.BSP could reduce friction by forming hydration layer.The nanoscale three-dimensional network structures enable BSP to maintain high water retention and absorb strongly on bentonite and metal surface,contributing to enhanced rheology,filtration,inhibition and lubrication properties.The versatile characteristic of BSP,as well as biodegradation makes it a promising additive using in high performance water-based drilling fluid and a potential alternative to conventional synthetic polymers.

Super-amphiphobic, strong self-cleaning and high-efficiency water-based drilling fluids

Based on the amphiphobic theory on underground rock surface, a super-amphiphobic agent is developed and evaluated which can form nano-micro papilla structure on rock, filter cake and metal surface, reduce surface free energy, prevent collapse, protect reservoir, lubricate and increase drilling speed. With this super-amphiphobic agent as the core agent, a super-amphiphobic, strong self-cleaning and high-performance water-based drilling fluid system has been developed by combining with other agents based on drilled formation, and compared with high-performance water-based drilling fluid and typical oil based drilling fluid commonly used in oilfields. The results show that the super-amphiphobic, strong self-cleaning and high-performance water-based drilling fluid has better rheology, and high temperature and high pressure filtration similar with that of oil-based drilling fluid, inhibiting and lubricating properties close to oil based drilling fluid. Besides, the super-amphiphobic system is non-toxic, safe and environmentally friendly. Field tests show this newly developed drilling fluid system can prevent wellbore collapse, reservoir damage and pipe-sticking, increase drilling speed and lower drilling cost, meeting the requirement of safe, high efficient, economic and environmentally friendly drilling. Compared with other drilling fluids, this new drilling fluid system can reduce downhole complexities by 82.9%, enhance the drilling speed by about 18.5%, lower drilling fluid cost by 39.3%, and increase the daily oil output by more than 1.5 times in the same block.

Preparation and Performance of the Hyperbranched Polyamine as an Effective Shale Inhibitor for Water-Based Drilling Fluid

Seeking effective solutions to control and mitigate the interaction between drilling fluids and clay formations has been a challenge for many years, and various shale inhibitors have shown excellent results in problematic shale formations around the world. Herein, the hyperbranched polyamine (HBPA) inhibitor with a higher ratio of amine groups and obvious tendentiousness in protonation was successfully synthesized from ethylenediamine, acryloyl chloride and aziridine by five steps, in which the metal-organic framework (MOF) was employed as a catalyst for ring-open polycondensation (ROP). The structure and purity were confirmed by nuclear magnetic resonance hydrogen spectroscopy and high-performance liquid chromatography (HPLC) respectively. The HBPA displays more excellent performance than EDA and KCl widely applied in the oil field. After aging at 80°C and 180°C, the YP of a slurry system containing 25 wt.% bentonite and 2 wt.% HBPA are just 8.5 Pa and 5.5 Pa (wt.%: percentage of mass), respectively. The swelling lengths of 2 wt.% HBPA are estimated to be 1.78 mm, which falls by 70% compared with that of freshwater. Under a hot rolling aging temperature of 180°C, the HBPA system demonstrates a significant inhibition with more than 85% shale cuttings recovery rate and is superior to conventional EDA and KCl. Mechanism analysis further validates that the HBPA can help to increase the zeta potential.

A high-temperature resistant and high-density polymeric saturated brine-based drilling fluid

Three high-temperature resistant polymeric additives for water-based drilling fluids are designed and developed:weakly cross-linked zwitterionic polymer fluid loss reducer(WCZ),flexible polymer microsphere nano-plugging agent(FPM)and comb-structure polymeric lubricant(CSP).A high-temperature resistant and high-density polymeric saturated brine-based drilling fluid was developed for deep drilling.The WCZ has a good anti-polyelectrolyte effect and exhibits the API fluid loss less than 8 mL after aging in saturated salt environment at 200°C.The FPM can reduce the fluid loss by improving the quality of the mud cake and has a good plugging effect on nano-scale pores/fractures.The CSP,with a weight average molecular weight of 4804,has multiple polar adsorption sites and exhibits excellent lubricating performance under high temperature and high salt conditions.The developed drilling fluid system with a density of 2.0 g/cm^(3)has good rheological properties.It shows a fluid loss less than 15 mL at 200°C and high pressure,a sedimentation factor(SF)smaller than 0.52 after standing at high temperature for 5 d,and a rolling recovery of hydratable drill cuttings similar to oil-based drilling fluid.Besides,it has good plugging and lubricating performance.

Mechanism of shales stabilization by hydrophobized poly(ethylene glycol)/K^(+) in water-base drilling fluids

The mechanism of the hydrophobized poly(ethylene glycol)(PEG)/K^(+) system inhibiting shale hydration was studied by laboratory experiment. The inhibition performance was evaluated through cuttings hot-rolling dispersion, bentonite inhibition and contact angle tests. The inhibition became stronger as contact angle and PEG concentration increased. A modified cuttings hot-rolling dispersion experiment suggested that these molecular systems did not act through the thermally activated mud emulsion(TAME) mechanism. The interaction of the PEG/K^(+) with clay samples was investigated through adsorption studies and by Fourier transform infrared spectroscopy(FT-IR), X-ray diffraction(XRD) and thermogravimetric analysis(TGA). The adsorption isotherms showed that the presence of K^(+) increased the PEG affinity for the clay surface. This inhibition effect was accompanied by a reduction of the bentonite hydration with PEG adsorption, evidenced by FT-IR, TGA and differential thermogravimetric(DTG) curves. XRD patterns were conclusive in showing that the presence of K^(+) ions limited the expansion of the clay interlamellar region to only one PEG layer, and the terminal hydrophobic segments of the PEG chains turned out to be determinant in enhancement of the inhibitory efficiency. The cuttings hot-rolling dispersion was carried out on water-base drilling fluid with PEG/K^(+), which proved the inhibition performance of PEG/K^(+) in oil field drilling.

Natural rubber latex as a potential additive for water-based drilling fluids

The environmental hazards and"carbon footprint"of oil and gas drilling can be significantly reduced by replacing traditional petroleum-based chemical additives with natural materials derived from plants and animals.This paper explored for the first time the interaction mechanism between natural rubber latex(NRL)and bentonite suspensions(BTs)through a series of characterization experiments,as well as the potential applications in water-based drilling fluids(WBDF).The gel viscoelasticity experiments showed that NRL could decrease the consistency coefficient(k)and flow index(n)of BTs,and enhance the shear thinning performance of BTs as pseudo-plastic fluids.In addition,0.5 w/v%NRL not only increased the critical yield stress and strengthened the structural strength between the bentonite particles,but also facilitated the compatibility of pressure loss and flow efficiency.The evaluation of colloidal stability and WBDF performance indicated that NRL particles could promote the hydration and charge stability on the surface of BTs particles,and optimize the particle size distribution and flow resistance of WBDF under the"intercalation-exfoliation-encapsulation"synergistic interaction.Moreover,NRL can improve the rheological properties of WBDF at high temperatures(<150.C),and form a dense blocking layer by bridging and sealing the pores and cracks of the filter cake,which ultimately reduces the permeability of the cake and the filtration loss of WBDF.

Performance evaluation of laponite as a mud-making material for drilling fluids

In this study, laponite was tested as a mud-making material for drilling fluids. Laponite is a synthetic smectite clay with a structure and composition closely resembling the natural clay mineral hectorite. Commercially available laponite was characterized by X-ray di ractometry, scanning electron microscopy and infrared spectrometry. Its dispersibility, salt resistance and high-temperature resistance were evaluated. The results showed that laponite possessed superior cation exchange capacity(140.4 mmol/100 g) with interlayer cations of Na^+ and Li^+. Laponite could easily be dispersed in water to yield increased viscosity with no influence from hydration time or temperature. On the other hand, laponite dispersions displayed an excellent heat resistance, with invariant apparent viscosity at high temperatures. For instance, the apparent viscosity of the2 wt% laponite dispersion underwent changes between 22 and 24 mPa s after hot rolling at 180–240 °C for 16 h. Compared to existing mud-making materials, laponite exhibited better mud-making properties. Furthermore, laponite revealed good compatibility with other additives, and the water-based drilling fluids prepared with laponite as mud-making material showed an excellent stability at elevated temperatures and superior performance–cost ratios. Overall, these findings indicated that laponite had an excellent dispersibility at high temperatures and hence would have promising applications as high-temperature mud-making material for preparing water-based drilling fluids designed for ultra-high-temperature environments.

Influence of monoethanolamine on thermal stability of starch in water based drilling fluid system

To improve the thermal stability of starch in water-based drilling fluid,monoethanolamine(MEA)was added,and the effect was investigated by laboratory experiment.The experimental results show that the addition of monoethanolamine(MEA)increases the apparent viscosity,plastic viscosity,dynamic shear force,and static shear force of the drilling fluid,and reduces the filtration rate of drilling fluid and thickness of mud cake apparently.By creating hydrogen bonds with starch polymer,the monoethanolamine can prevent hydrolysis of starch at high temperature.Starch,as a natural polymer,is able to improve the rheological properties and reduce filtration of drilling fluid,but it works only below 121℃.The MEA will increase the thermal stability of starch up to 160℃.There is a optimum concentration of MEA,when higher than this concentration,its effect declines.

The influence of water-based drilling fluid on mechanical property of shale and the wellbore stability

Because of high cost and pollution of oil-based drilling fluid,the water-based drilling fluid is increasingly used now.However,bedding planes and micro-cracks are rich in shale formation.When water-based drilling fluid contacts formation rock,it causes the propagation of crack and invasion of drilling fluid,which decrease shale strength and cause wellbore instability.In this paper,we analyzed influence of water-based drilling fluid on shale strength and failure mode by mechanics experiment.Based on those experimental results,considering the effect of bedding plane and drilling time,we established modeling of wellbore stability for shale formation.The result from this model indicates that in certain azimuth of horizontal well,collapsing pressure increases dramatically due to shale failure along with bedding plane.In drilling operation,those azimuths are supposed to be avoided.This model is applicable for predication of collapsing pressure in shale formation and offers reference for choosing suitable mud weight.

Minimizing the filtration loss of water-based drilling fluid with sustainable basil seed powder

Filtration control is important to ensure safe and high efficient drilling.The aim of the current research is to explore the feasibility of using basil seed powders(BSPs)to reduce filtration loss in water-based drilling fluid.The effect of BSP concentration,thermal aging temperature,inorganic salts(NaCl and CaCl_(2))on the filtration properties of bentonite/basil suspensions was investigated.The filtration control mechanism of BSP was probed via water absorbency test,zeta potential measurement,particle size distribution measurement,and filter cake morphologies observation by scanning electron microscope.The incorporation of BSPs into the bentonite suspension generated acceptable rheology below 1.0 w/v%.The BSPs exhibited effective filtration control after thermal aging at 120C,but less efficiency at 150C.After thermal aging at 120℃,the bentonite suspension containing 1.0 w/v%BSPs could resist NaCl and CaCl_(2) pollution of 5.0 w/v%and 0.3 w/v%respectively.Besides general filtration control behaviors,the exceptional water retaining capability formed by numerous nanoscale 3D networks in the basil seed gum and considerable insoluble small particles in BSPs might further contribute to the filtration control.The excellent filtration properties bring basil seed a suitable and green candidate for the establishment of high-performance drilling fluids.