Performance of water-based drilling fluids for deepwater and hydrate reservoirs:Designing and modelling studies

In deepwater drilling,the properties of water-based drilling fluids change remarkably due to low temperature and high pressure,which have a significant effect on lost circulation,wellbore instability and the window between pore pressure and fracturing pressure.The present work investigates the influence of low temperature and high pressure on polymer and nanoparticle(boron nitride(BN))based drilling fluids with an aim to improve their rheological properties and fluid loss control.The amplitude and frequency sweep tests were conducted to understand the viscoelastic nature of the samples.The amplitude sweep tests confirmed the structural stability of the designed fluid within the studied sweep frequency.The study reveals that storage modulus(G')and loss modulus(G")of the samples are enhanced with increasing concentration of BN nanoparticles.Their viscoelastic range also increases due to the intermolecular interaction within the structure of the fluid in the presence of the nanoparticles.Within the linear viscoelastic range(LVER),all the samples show the dominance of elastic modulus than viscous modulus which delineates the solid-like behaviour.The results of rheological tests of drilling fluid containing BN nanoparticles indicate a significant reduction in plastic viscosity(PV),yield point(YP)and apparent viscosity(AV).The rheological studies conducted at different temperatures(from 10℃to-5℃)and pressures(from 7.8 MPa toll MPa)reveal the minimum effect of pressure and temperature on the rheology of samples,which are desirable for their applications in hydrate and deepwater drilling.The filtration loss experiments conducted at 30℃and 0.69 MPa show a large reduction in fluid loss volume(60.6%)and filter cake thickness(90%)for the sample with 0.4 wt%BN nano particles compared to that of the sample without nanoparticles.The filter cake permeability is also in the favourable range with0.008 mD which shows a 94%reduction compared to the sample without nanoparticles.A regression model was developed to mathematically describe the experimental results,which demonstrates a good fitting with the statistical data of fluid loss volume,thickness and permeability of the filter cake.

A nano-particle based approach to improve filtration control of water based muds under high pressure high temperature conditions

There have been many attempts to improve the filtration control of water based muds under High Pressure High Temperature(HPHT)condition using a cost effective approach.Nano particles are perhaps the best option considering their successful applications reported in many studies.However,they are often expensive and pose unfavourably changes on the rheology of the muds.In this paper,an attempt was made to show the application of Nano Glass Flakes(NGFs)as a cheap but effective nano particle to control the filtration of water based muds under HPHT conditions.Performing a series of rheology,filtration and conductivity tests on the mud samples with unmodified NGFs revealed that this nano particle increases the mud rheology,yield point and gel strength of the mud with a slight impact on the filtration loss.However,by modifying the surface charges of NGFs with a cationic surfactant,filtration loss was significantly reduced without any severe impacts on the mud rheology.Considering the conductivity of the mud which increases by adding the modified NGF,this nano particle might be a good choice to improve the overall performance of water based muds under HPHT conditions.

Experimental investigation of the impact of sugarcane molasses on the properties of colloidal gas aphron(CGA)drilling fluid

Colloidal gas aphron(CGA)based fluid has become very popular in drilling in the last two decades,as it reduces formation damages significantly.In this study,sugarcane molasses(Mls)was used for the first time as a polymer in CGA-based to investigate its ability to improve the role of aphronized fluid as a drilling fluid.The results showed that increasing the concentration of Mls to 12%(v/v)in CGA-based fluid reduces the drainage rate and increases half-life to 10.6 min,resulting in enhanced stability of the aphronized fluid.Also,because of increasing Mls concentration from 1%to 12%(v/v),the yield and the initial gas hold-up decrease to 74%and 299.4 mL,respectively,indicating that the presence of Mls allows less air into the aphron system.Although the rheological properties were improved in this study,the gel strength did not change considerably.Furthermore,the results showed that by increasing the concentration of Mls,the average size of the bubbles decreases,and the particle-size distribution becomes more uniform.Finally,the API filtration test revealed that the higher the Mls concentration in the aphronized fluid,the lower the fluid loss,and at the Mls concentration of 12%(v/v),the fluid loss was estimated at 19.54 mL.A natural polysaccharide with high molecular weight,Mls can be used as a polymer in CGAbased fluid and,thus,improve its performance.