Thermal and Rheological Properties Improvement of Oil-based Drilling Fluids Using Multi-walled Carbon Nanotubes (MWCNT)

In this paper, we detail our results for the impact of MWCNT on the thermal and rheological properties of oil-based drilling muds. Our analysis considers the effects of time, temperature, and MWCNT volume fraction. The scanning electron microscopy imaging technique was used to monitor the MWCNTsdispersion quality. The experimental results unveil a considerable enhancement in the thermal conductivity of the MWCNT-oil-based mud by 40.3% (and 43.1% in case of functionalized MWCNT) and 1% vol. MWCNT. The rheological properties results for the MWCNT-oil-based mud exhibit a similar (improvement) trend by reducing annular viscosity and increasing yield point and gel strength. The high-temperature high-pressure filtration tests conducted at 280°F and 500 psi show a  reduction of 16.67% for the filtrate amount in case of MWCNT-oil-based mud (with 1% vol. MWCNT). The effect of time on thermal conductivity reduction in both unfunctionalized and functionalized systems was observed to equalize (at 9.7%), after 100 hours of sample preparation. The performance results of MWCNT-oil-based mud are presented for an actual industrial drilling operation case.</span

The effect of cations on gelation of cross-linked polymers

The effects of different cation concentrations and types on rheological property and stability of Guar, Xanthan, and Partially Hydrolyzed Polyacrylamide (HPAM) cross-linked gels were analyzed through experiments. Also, a new approach was developed to reduce the negative effects of cation by application of multi-walled carbon nano-tubes (MWCNTs). The presence of cations in cross-linked gel system will reduce the viscosity of gel, the higher the cation concentration is, the lower the viscosity will be. The bivalent cation has a greater viscosity reduction effect on gel than monovalent cation. The stability of cross-linked gels is worse with cations, this situation becomes more serious under higher salinity. MWCNTs were added to HPAM gel, cross-linked by (3-Aminopropyl) triethoxysilane (APTES), they surrounded cations and removed them from polymers and reduced the reaction possibility. This method enhances the viscosity and breakdown pressure of cross-linked gels, improves the stability of HPAM cross-linked gel under different operating conditions, and can be applied to related drilling projects

SOLID GEO MECHANICAL INVESTIGATION OF THE EFECT OF SALT CREEP ON CASING STABILITY USING FNITE ELEMENT METHOD: A CASE STUDY

The salt formation creeping can signifcantly afect the casing stability, because of the changes in mechanical and geome chanical parameters. The creeping of Gachsaran salty formation in the south part of Iran has infuences on wells drilled in the region, which should be carefully considered in the casing design process. In this study, the fnite element analysis technique was applied to study the alteration in mechanical/geomechanical parameters of a well in this formation. The accuracy of the methodology was validated by data available from the reduction in wellbore diameter of another well in the formation. Diferent scenarios were studied to analyze the efect of geomechanical parameters on stress, plastic strain, and casing diameter for a cased cemented well and a well completed with two casings. The efect of mechanical parameters on casing collapse was studied, where casing eccentricity, ovality, and slenderness ratio were also considered. Our simulation studies showed that casing stability in salty formations is strongly afected by geomechanical and pipe mechanical parameters. To reduce the severity of the casing collapse in salty formation, it is recommended to complete the well with two casings. Our study showed that, this arrangement reduces the plastic strain and the change in casing diameter signifcantly For a safe casing design, efect of mechanical parameters should be also considered. Efects of parameters such as ovality, eccentricity, and slenderness ratio are noticeable, for example, 2% ovality and 2% eccentricity in L-80 casing, lead to increase in the plastic strain from 0.112 to 0.31 and 0.3, and the overall diameter reduction from 0.455″ to 0.685″ and 0.535″, respectively

An Improvement in Thermal and Rheological Properties of Water-based Drilling Fluids Using Multiwall Carbon Nanotube (MWCNT)

Designing drilling fluids for drilling in deep gas reservoirs and geothermal wells is a major challenge. Cooling drilling fluids and preparing stable mud with high thermal conductivity are of great concern. Drilling nanofluids, i.e. a low fraction of carbon nanotube (CNT) well dispersed in mud, may enhance the mixture thermal conductivity compared to the base fluids. Thus, they are potentially useful for advanced designing high temperature and high pressure (HTHP) drilling fluids. In the present study, the impacts of CNT volume fraction, ball milling time, functionalization, temperature, and dispersion quality (by means of scanning electron microscopy, SEM) on the thermal and rheological properties of water-based mud are experimentally investigated. The thermal conductivities of the nano-based drilling fluid are measured with a transient hot wire method. The experimental results show that the thermal conductivity of the water-based drilling fluid is enhanced by 23.2% in the presence of 1 vol% functionalized CNT at room temperature; it increases by 31.8% by raising the mud temperature to 50 °C. Furthermore, significant improvements are seen in the rheological properties—such as yield point, filtration properties, and annular viscosity—of the CNTmodified drilling fluid compared to the base mud, which pushes forward their future development

The effect of cations on gelation of cross-linked polymers

The effects of different cation concentrations and types on rheological property and stability of Guar, Xanthan, and Partially Hydrolyzed Polyacrylamide (HPAM) cross-linked gels were analyzed through experiments. Also, a new approach was developed to reduce the negative effects of cation by application of multi-walled carbon nano-tubes (MWCNTs). The presence of cations in cross-linked gel system will reduce the viscosity of gel, the higher the cation concentration is, the lower the viscosity will be. The bivalent cation has a greater viscosity reduction effect on gel than monovalent cation. The stability of cross-linked gels is worse with cations, this situation becomes more serious under higher salinity. MWCNTs were added to HPAM gel, cross-linked by (3-Aminopropyl) triethoxysilane (APTES), they surrounded cations and removed them from polymers and reduced the reaction possibility. This method enhances the viscosity and breakdown pressure of cross-linked gels, improves the stability of HPAM cross-linked gel under different operating conditions, and can be applied to related drilling projects

EXPERIMENTAL INVESTIGATION OF THE APPLICATION OF EUCALYPTUS BARK TO PREVENT LOST CIRCULATION IN PAY ZONES WITH ACID DISSOLUTION CAPABILITY

Loss of drilling fluid is a common problem during the drilling of wells and it restricts the appropriate functionality of muds. Drilling fluid loss significantly increases drilling costs and non-productive time as well as the drilling operation risks. Various investigations have been carried out in order to find appropriate mud additives that either block fractures and pores or reduce fluid loss by improving the fluid rheology. Cheap, environmentally friendly and effective additives are still required by the drilling industry. Hence, the application of available materials in each region, to produce appropriate additives, is a challenge for the oil industry. In this study, Eucalyptus Camaldulensis (EUC) bark powder has been chosen as a new, fibrous, cheap, environmentally friendly and available material to control fluid loss, particularly in southern Iran. Different characterization tests, such as acid dissolution and fluid loss control, were carried out to study the performance of the new proposed additive. Removal by hydrochloric acid and sulfuric acid were studied at various acid concentrations and temperatures. Dynamic fluid loss was also measured at different EUC concentrations. Our study showed that EUC powder can reduce the final fluid loss by 88–97%, the initial fluid loss by 45–66%, and the total loss by 87–94%, which is a satisfactory level

An approach for optimization of controllable drilling parameters for motorized bottom hole assembly in a specific formation

This study focuses on optimizing drilling parameters when using Positive Displacement Motors (PDMs). In drilling operations involving mud motors, weight-on-bit (WOB) alterations lead to variations in the system's parasitic pressure drop. Consequently, this affects the optimum flow rate and the hydraulic power of the bit. Also, if the flow rate changes, the bit's rotations per minute (RPM) also change. In other words, using PDMs creates a link between the hydraulic system and the drilling speed, such that changing drilling parameters such as the WOB causes changes in the hydraulic system's performance. Therefore, one possible way to optimize the drilling parameters is to consider the drilling rate and hydraulic system simultaneously using a multi-objective approach. This study used an integrated approach encompassing data mining and mathematical modeling, employing a multi-objective framework to identify optimal parameters. The approach was applied to Dariyan Formation drilling data. The data mining approach revealed a well-distributed data set covering optimal and suboptimal zones suitable for optimization. In data mining, the identification of optimal conditions included a WOB of 11500 lb, a rotation speed of 105.8 rev/min, and a flow rate of 843 gpm, leading to an ROP of 44.23 ft/h. In multi-objective optimization, the optimal parameters consisted of a WOB of 14480 lb, a rotation speed of 115 rev/min, and a flow rate of 920.8 gpm, resulting in an ROP of 40.49 ft/h. Comparing optimal results with the drilling data shows a substantial MSE reduction of over 35 %. The results show the good performance of this approach in detecting the optimal and non-optimal drilling variables