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.

Fabrication of a Hydrophobic Hierarchical Surface on Shale Using Modified Nano-SiO_(2)for Strengthening the Wellbore Wall in Drilling Engineering

Wellbore stability is essential for safe and efficient drilling during oil and gas exploration and development.This paper introduces a hydrophobic nano-silica(HNS)for use in strengthening the wellbore wall when using a water-based drilling fluid(WBF).The wellbore-strengthening performance was studied using the linear swelling test,hot-rolling recovery test,and compressive strength test.The mechanism of strengthening the wellbore wall was studied by means of experiments on the zeta potential,particle size,contact angle,and surface tension,and with the use of a scanning electron microscope(SEM).The surface free energy changes of the shale before and after HNS treatment were also calculated using the contact angle method.The experimental results showed that HNS exhibited a good performance in inhibiting shale swelling and dispersion.Compared with the use of water,the use of HNS resulted in a 20%smaller linear swelling height of the bentonite pellets and an 11.53 times higher recovery of water-sensitive shale—a performance that exceeds those of the commonly used shale inhibitors KCl and polyamines.More importantly,the addition of HNS was effective in preventing a decrease in shale strength.According to the mechanism study,the good wellbore-strengthening performance of HNS can be attributed to three aspects.First,the positively charged HNS balances parts of the negative charges of clay by means of electrostatic adsorption,thus inhibiting osmotic hydration.Second,HNS fabricates a lotus-leaf-like surface with a micro-nano hierarchical structure on shale after adsorption,which significantly increases the water contact angle of the shale surface and considerably reduces the surface free energy,thereby inhibiting surface hydration.Third,the decrease in capillary action and the effective plugging of the shale pores reduce the invasion of water and promote wellbore stability.The approach described herein may provide an avenue for inhibiting both the surface hydration and the osmotic hydration of shale.

Experimental evaluation of thiamine as a new clay swelling inhibitor

This study aims at evaluating the performance of thiamine as a new eco-friendly shale inhibitor in water-based drilling fluids(WBDFs).The evaluation experiments include sedimentation,bentonite inhibition,filtration,zeta potential,thermal gravimetric analysis,scanning electron microscopy,X-ray diffraction,shale cuttings recovery,linear swelling and Fourier transform infrared spectroscopy(FTIR).The performance of thiamine was compared to potassium chloride.In contrast to deionized water,the aqueous solution of thiamine exhibited greater power to inhibit montmorillonite(Mt)dispersion,much more Mt loading capacity(280 g/L)and fluid loss,lower Mt mass loss,larger aggregated Mt particles,lower interlayer space of the Mt particles,less shale cuttings disintegration and lower linear swelling.Adsorption of thiamine on Mt led to a significant shift in the value of zeta potential(from-17.1 to+8.54 mV).Thiamine demonstrated superior inhibitive performance than potassium chloride.FTIR analysis confirmed that thiamine is adsorbed on Mt particles.The compatibility test revealed the compatibility of thiamine with conventional WBDF additives.It was concluded that the main probable inhibition mechanisms of thiamine are the cation exchange and Mt surface coating.In view of its prominent inhibition capacity and great environmental acceptability,thiamine is a promising inhibitor for drilling in water-sensitive formations.

RESEARCH ON CATIONIC POLYMER WATER BASE DRILLING FLUIDS

Cationic polymer drilling fluid (CPDF) is a new water base drilling fluid in which high molecular weight (HMW) cationic polymer (CPAM) is an encapsulating and flocculating agent and organic quaternary ammonium compound (NW-1) acts as shale inhibitor. This paper describes the experimental results of cuttings recovery, particle size distribution layer spacing and Zeta potential, and discusses the inhibition of CPDF system and its major additives. The advantages of CPDF will be proved by its application in well LX-2.

Application status and prospect of ionic liquids in oilfield chemistry

The ionic liquid,as a new treatment agent,has been increasingly applied in oil fields due to its strong temperature resistance,good solubility and high surface activity.In this paper,we systematically discuss the action mechanism and application effect of ionic liquids in oilfield chemistry.Ionic liquids can inhibit shale hydration expansion and reduce fluid loss through adsorption and intercalation,inhibit the formation of natural gas hydrate through imidazole five-membered ring structure as a space barrier,reduce viscosity of heavy oil by breaking chemical bonds of heavy oil macromolecules and charge transfer,improve oil displacement efficiency by forming ions pairs with carboxyl groups in crude oil,demulsify by forming channels between dispersed water droplets,acidify the formation by reacting with water to produce acid,interacts with organic material through weak hydrogen bonds and extracts it from oilfield wastewater,desulphurize by inserting sulfide molecules into the“stack”structure and form liquid inclusion complex,inhibit corrosion by forming a protective film on the metal surface.Based on the above aspects,the development direction of ionic liquids is proposed.The application of ionic liquids in oilfield chemistry is still in its infancy.It is urgent to fully explore the application performance of ionic liquids in oilfield chemistry,which also provides theoretical and technical supports for efficient reservoir development.

Integrated feasibility analysis of shale inhibition property by utilization of pore pressure transmission equipment

Regarding the widespread utilization of formate-based drilling fluids in numerous operational circumstances,petroleum industries are in urgent need of decreasing wellbore inefficiencies by improving the procedures quality.Thereby,providing appropriate parameters such as safety,boosting the drilling speed and enrolling the proper procedure of optimizing performances of high activity water-sensitivity formation should be taken into consideration.The objective of this comprehensive study is to apply experimental evaluation tests on the shale inhibitor fluids by using prepared plug samples from the studied field due to the administration of pore pressure transmission(henceforth,PPT)equipment.Even though,PPT equipment is not able to simulate all the mechanisms which are applied to different drilling fluids on the shale layers’stability,it will control such parameters like the penetration of fluid filtration through the formation that subsequently reduce the wellbore problems.Consequently,the ubiquitous use formate fluid in drilling operations of exploratory oil wells in the studied field is successfully implemented to be addressed the current well inefficiencies adequately.

A natural dye in water-based drilling fluids: Swelling inhibitive characteristic and side effects

The development of eco-friendly shale inhibitors is still an area which has attracted a lot of attention in the drilling industry.Henna extract is a natural dye which has recently shown considerable inhibition and weak deflocculation properties in clay-water system.This study aims to investigate swelling inhibitive feature and side effects of Henna extract in water-based drilling fluids(WBDFs).It was carried out through extensive experiments including adsorption measurements on shale by batch equilibrium,inhibition evaluation by dynamic linear swelling and cuttings dispersion,wettability alteration via contact angle measurements,compatibility by rheological properties determinations and fluid loss measurements,and lubricity.Both in natural pH and adjusted pH to 9,Linear adsorption model was more suitable for anticipating the adsorption behavior of Henna extract on the given shale sample.The results of the linear swelling and cuttings dispersion tests demonstrated that Henna extract in drilling fluid formulations diminished the swelling and dispersion characteristics of the addressed shale sample.Moreover,contact angle measurements showed that Henna extract expanded the hydrophobicity of shale formations,preventing and promoting water adsorption and shale stability respectively.This issue definitely introduces wettability alteration as a mechanism for shale stability by Henna extract.Compatibility determinations additionally uncovered that Henna extract is compatible with common WBDFs additives.As indicated by the lubricity tests,Henna extract enhanced the lubricity of WBDFs,a finding which can be of an incredible significance in directional drilling.Among others,advantages such as environmental friendliness,low cost,accessibility,and the counter corrosion property make the applicability of Henna extract in WBDFs profoundly suitable.