Cuttings transport is a topic of great interest in the oil and gas drilling industry. Insufficient cuttings transport leads to several expensive problems. Knowledge and selection of the drilling fluids is one of the important factor for efficient hole cleaning. It has been observed, however, that the hole cleaning performance of drilling fluids can be different even if the fluid rheological properties are similar as measured in accordance with API specifications. The reasons for stated difference in the behavior of drilling fluids are not well understood. The main objective of present work is to evaluate hole cleaning efficiency of an oil-based drilling fluid (OBM) and a water-based drilling fluid (WBM) whose viscosity profiles are similar as per API specifications.Hole cleaning efficiency of an oil-based drilling fluid and a water-based drilling fluid whose rheological properties are similar was investigated. The fluids tested were industrial fluids used in the field and were sent to us after reconditioning. Experimental studies were performed on an advanced purpose-built flow-loop by varying flow velocities and drill string rotation rates. The flow loop had a 10 m long annulus section with 4" inner diameter wellbore and 2" outer diameter fully eccentric drill string. Pressure drop and sand holdup measurements were reported. Rheological investigations of the same fluids were used to understand the difference in the behavior of the drilling fluids tested. Higher pressure drop was observed for WBM compared to OBM, and for both fluids, the pressure drop increased with drill string rotation speed. In case of no drill string rotation, better hole cleaning performance was observed with the oil-based fluid compared to the water-based fluid. With the presence of drill string rotation, hole cleaning performance of both the fluids was nearly the same.
Hole cleaning is still among the most important problems to handle in drilling operations. The difficulty in removing cuttings bed during drilling arises because of the drilling fluid interacts with the cuttings in cuttings bed to form a cuttings bed gel. The drilling fluid composition can be designed to minimize the gel formation in the cuttings bed. At the same time the drilling fluid properties are optimized to ensure a sufficient shear stress on the cuttings particles to be able to remove the cuttings. This technique has been used in several of Statoil's drilling operations. The paper explains the effect of the cuttings bed properties on hole cleaning in detail. Furthermore, the paper demonstrates how the drilling operations were improved compared to earlier drilling operations using conventional drilling fluids. From drilling operations in North Sea fields it is shown how the total drilling progress is improved. The torque curves of comparable wells are shown. These curves demonstrate that a significantly improved hole cleaning have been experienced in the wells drilled with the drilling fluid made to minimize cuttings bed gel formation. Introduction Although large resources have been spent on studying hole cleaning, there is still a debate going on how to optimize hole cleaning properties. The necessity of understanding hole cleaning is caused by the different operational problems that can arise if sufficient hole cleaning is not achieved. Poor hole cleaning may result in lost circulation or hinder the casing or liner to be run into its selected position. Therefore, it is important to use the correct operational practice to ensure optimum hole cleaning. Presently, recommendations to obtain good hole cleaning vary, depending on the different experiences or other sources that the recommendation is based. Recently, it has been recognized that the cuttings bed consolidation properties are important in evaluating the potential for hole cleaning1. Although these properties has not been fully implemented in practical evaluation during the drilling operation, the properties have been used indirectly in modeling hole cleaning ability through the use of necessary shear stress at the cuttings bed surface to remove cuttings2. Oil based and water based drilling fluids have been found to act differently in respect to hole cleaning even though their viscosity profiles may have been fairly equal. The different behavior is caused by the different ways these drilling fluids are constructed. Oil based drilling fluids are formulated using a continuous oil phase. The oil based drilling fluids are viscosified by the addition of emulsified water, typically in concentrations between 15 and 25% and by the addition of organophilic clay. There is no contact between the cuttings and the water when drilling with oil based drilling fluids. In water based drilling fluids a brine phase is viscosified by different polymers. These polymers will couple the fluid to the cuttings and thereby create a possibility for the fluid to generate a more or less consolidated cuttings bed. In the present paper there is an evaluation of the effect of the drilling fluid rheological properties of water based drilling fluids on hole cleaning properties in deviated wells. Although the effects on the cuttings bed are different when oil based drilling fluids are used, there are a few conclusions that can be generalized from the water based drilling fluid case to also be valid for drilling with oil based drilling fluids. These generalizations are also summarized in the article. The evaluation presented in the present article is based on results from several wells from different fields in the North Sea. In these wells the well paths include most sections from the more problematic 45°-70° deviations to horizontal sections were saltation flow could help simplifying hole cleaning. It is recognized from investigations that drill pipe rotation has positive effects on hole cleaning3. In practical operations, drill pipe rotation is well known to give better hole cleaning.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.