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PETROMAKS2-Stort program petroleum

Optimized hydraulic behaviour in well construction

Alternative title: Optimalisering av brønnhydraulikk

Awarded: NOK 16.4 mill.

When constructing oil and gas wells drilling fluid flows down the drill string and up in the drilled hole outside. Drilling fluid must keep the well pressure under control, prevent hole collapse and transport the cuttings to the surface. The latter is known as hole cleaning. The drilling industry experience challenges due to insufficient hole cleaning - meaning that drill cuttings are not transported out of the well with sufficient efficiency. This is mainly a problem in highly deviated well sections where the gravity is close to perpendicular to the fluid flow direction. Remnant cuttings bed can reduce drilling progress. After the drilling operation a casing is set into the well and this must be cemented to the formation to isolate different pressure zones. Presence of remnant cuttings can make cementing operations difficult. The projects key objective is to improve understanding of vital hydraulic operations during well construction. This project addresses the knowledge on these key issues through fundamental and experimental work for improved access to controlled data. The data will be analyzed and new insights will be applied directly. Data will also be used for model validation and improvements in relevant digital platforms. One PhD will validate and develop digital model while another PhD will characterize drilling fluids and their cuttings bed properties. Unique experimental equipment representing a wellbore with relevant oil- and water-based drilling and completion fluids will be applied in the experiments. An improved description of the Herschel-Bulkley viscosity model for pressure loss estimation is developed. This model is highly relevant for the industry, and the improvement opens for digitalizing the inputs like drilling fluid composition and changes during application. This model is now expanded for pressure drop calculations. Experimental results support that oil-based drilling fluids provides more efficient cuttings transport in highly deviated sections than water based fluids with similar properties. Experimental results in several small scale setups also show that the cuttings bed cohesive strengths are highly dependent to the properties of original carrier fluid. Polymer based fluids give a higher cohesive strength compared to other fluids like oil-based drilling fluids. Experiments show that the presence of remnant cuttings bed in annulus may cause a poorer displacement also down stream this obstacle. This indicates that elements below the inner pipe in the annulus can have significant impact on the displacement process. Such issues may need to be further assessed to avoid problems and ensure proper zonal isolation. The project group consists of SINTEF, NTNU, UiS, University of Illinois and University of British Columbia. The results and experiences from the project will, in addition to optimize the drilling and completion fluid compositions, lead to improved fluid engineering models for field applications.

Operational challenges exist caused by insufficient hole cleaning. Drilling progress is reduced and cementing operations become difficult due to remnant cuttings in the borehole. There is also a knowledge gap and lack of digitalised models for planning and operation. The project focuses on these items and the key objective is to improve understanding of vital hydraulic operations during drilling and cementing. This project addresses the knowledge on these key issues through fundamental and experimental work for improved access to controlled data and through model work for field application of the results. A unique experimental equipment representing a wellbore with a drill-string, liner/casing or a completion string will be applied for the experimental tasks. The equipment is designed with a size suitable for scaling up the results for field application. Field specific oil and water based drilling and completion fluids from the Norwegian Continental Shelf (NCS) will be applied in this work. Results from the experimental campaigns, covering both cuttings transport and displacement for primary cementing, will be included in relevant digital platforms. An improved description of the Herschel-Bulkley viscosity model for determination of pressure losses has been developed. This model is highly relevant for the industry, and with the improvement, opens for digitalising the inputs like drilling fluid composition and changes during application. A project group consisting of experienced personnel from SINTEF, NTNU, UiS, University of Illinois, University of British Columbia and Schlumberger ensure that the project builds on the most updated competence available. Also, personnel from other well respected universities will join the project group and discuss findings and share results. The results and experiences from the project will, in addition to optimise the drilling and completion fluid compositions, lead to improved fluid engineering models for field applications.

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PETROMAKS2-Stort program petroleum