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Deepwater drilling presents significant issues and uncertainties, especially when there is no prior drilling experience in country or only limited offset information is available. Uncertainties about the drilling conditions create additional risk to operators and can cause project budget increases. Therefore, innovative technologies are often implemented to help ensure that the well is drilled efficiently and safely, operators obtain well data and important geological data that can help identify potential reservoirs and wells in the area. Petrobras Colombia undertook the challenge of drilling the first deepwater well in Tayrona BLock located in the Colombian Caribbean, in approximately 1,840 ft water depth. Drilling fluid selection was a key decision to the success of the project due to the nature of the exploratory project, formation uncertainty, environmental footprint, wellbore stability and protecting any potential reservoirs. A high-performance water-based fluid (HPWBF) was selected to drill the well based on the following criteria;The ability to discharge to the sea without environmental impactEffective inhibition capability to drill reactive clay formationsNon-dispersed, low-solids formulation to improve rate of penetration (ROP)Shear-thinning behavior for excellent hole cleaningHigh and low temperature as well as high-pressure stabilityLubricity, wellbore stability and low equivalent circulating density (ECD) values. The HPWBF provided excellent performance as demonstrated by trouble-free trips, casing, cementing and wireline logging operations. Rheological properties remained stable during changes in temperature and pressure, confirming reliable fluid stability and reducing costs associated with non productive time (NPT). Although the inhibition provided by the fluid system was excellent, the wellbore exhibited some mechanical instability related to stress distribution. No bit balling problems were observed and ROP was acceptable most of the time. Wiper trips required less time than expected and did not present any issues. In conclusion, the HPWBF demonstrated excellent performance in all aspects and contributed to the overall project success in obtaining important formation data, minimizing NPT and reducing costs related to fluid and cuttings disposal. Introduction Deepwater exploration activity in the oil and gas industry continues to present new hurdles requiring innovative technical solutions. These difficult wells can increase the risk factor and result in potentially higher operational costs. In most cases an oil-base drilling fluid is selected as the first option in light of the high daily costs associated with a deepwater operation, and the advantages gained in wellbore stability and ROPs compared to conventional water-based systems. However, tightening environmental regulations and high costs associated with cuttings and oily fluid disposal is sufficient to seek viable water base fluid alternatives that could yet provide an oil base drilling fluid performance. For this reason, drilling fluid companies constantly investigate and design state-of-the-art water based drilling fluid systems that can provide performance similar to an oil-based fluid but can be discharged directly to the sea with a reduced environmental footprint.

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The theme of this article is to scrutinize the entropy analysis for Darcy-Forchheimer flow of hybrid nanoliquid towards a stretched curved surface. Manganese and nickel (𝑀𝑛𝑍𝑛𝐹𝑒 2 𝑂 4 and 𝑁𝑖𝑍𝑛𝐹𝑒 2 𝑂 4 ) zinc ferrites are taken as nanoparticles. Here engine oil (𝐶 8 𝐻 18 ) is used as base liquid. Dissipation and radiation effects in energy equation are incorporated. The basic modeling of entropy analysis is developed through second law of thermodynamics. The governing nonlinear partial system (PDEs) of the flow are converted to ordinary one (ODEs) through utilizing suitable variable. The resultant system is consequently solved through one of numerical method (ND-solve method). Graphical illustrations of velocity field, thermal field and entropy rate versus dimensionless variables for both manganese and nickel zinc ferrites/engine oil nanoparticles are discussed. Computational results of Nusselt number and drag force for both 𝑀𝑛𝑍𝑛𝐹𝑒 2 𝑂 4 ∕𝐶 8 𝐻 18 and 𝑁𝑖𝑍𝑛𝐹𝑒 2 𝑂 4 ∕𝐶 8 𝐻 18 nanoparticles against flow parameters are studied in tabulated form. A reverse trend holds for velocity through curvature and porosity variables. Higher Forchheimer number diminishes the velocity profile. Larger approximation of radiation has similar effect on thermal field and entropy rate. Higher volume fraction enhances the entropy rate and velocity profile. An intensification in porosity variables rises entropy rate. An increment in drag force is noticed for volume fraction. Higher curvature variable improves the heat transfer rate.

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