Improved Hole Cleaning and Reduced Rotary Torque by New External Profile on Drilling Equipment

Abstract

This paper will describe the successful application and effects of completely new Hydro mechanical Cleaning and Hydrodynamic Bearing profiles machined externally on drilling equipment to improve hole cleaning and reduce rotary friction. Qualification programmes, including initial proving trials on a test rig, computational fluid dynamics and cuttings transportation flow loop tests, will supplement details from successful field operational use of this equipment. Introduction Drilling for Oil and Gas has reached the stage where it is more economical to drill an extended reach well to exploit reservoirs on the periphery of existing developments. Similarly, long horizontal sections through the reservoir are now the norm. The initial response to this need for extended reach drilling was to install top drives, upgrade the mechanical integrity of the drill string, and introduce larger outside diameter drill pipe with better materials and stronger connections. These improvements have been integrated into well design and now the limits are the amount of rotary torque and hydraulic power available to rotate the drill string and circulate sufficient drilling fluid to clean the well. The initial challenge was to build a sub which would reduce rotary drilling torque while maintaining the integrity of the drill string. In the initial design of the low torque sub an experimental Hydro mechanical cleaning zone was added. This tool proved to be very successful, showing up to 40% reduction in rotary torque. More importantly, the operator noticed improvements in hole cleaning. These included cuttings appearing at surface in close to theoretical bottoms up time, an increase in the size of cuttings, reduced pick-up and slack-off weights and improved steerability. The success of the Hydro mechanical hole cleaning design led to the development of heavy weight drill pipe and standard drill pipe with this feature. A critical part of the design of this Hydro mechanical cleaning drill pipe is that the cleaning zone is supported off the bore wall and only comes into contact with fluid or loose cuttings sedimentation. Success with concurrent field trials and testing led to the further development of the features described above and the addition of a dual upset tool joint to provide five bearing areas, each coated with industry standard hard facing material to control friction and wear. The remainder of this paper will describe the design principles, numerical modelling, application on drilling equipment, cuttings transport flow loop tests and on-going field operations of this HydrocleanTM System. Design Principles & Effects of New Profile Design & Functional Principles. (see fig. 1). The profile is designed with two different zones, the Hydro mechanical cleaning zone (HCZ) and the hydrodynamic bearing zone (HBZ), which interact and provide the two basic effects of the profile; hole cleaning and reduction of friction factor between the bearing areas on the modified drilling equipment and the bore wall. By design principles, the geometry of the profile modifies the trajectory of flowing lines in the annular passage, at the rotational speed ?, and the variation of geometry for drilling fluid passage, (either in terms of passage area or a combination of channel angles through which drilling fluid is forced to flow). There are two different alterations of flowing line patterns corresponding to the two different zones of the profile, where there is a Hydro mechanical cleaning effect and a hydrodynamic bearing effect. In order to have a better understanding of the effects developed by the profiles, the following will firstly describe the principles of the geometry. Design & Functional Principles. (see fig. 1). The profile is designed with two different zones, the Hydro mechanical cleaning zone (HCZ) and the hydrodynamic bearing zone (HBZ), which interact and provide the two basic effects of the profile; hole cleaning and reduction of friction factor between the bearing areas on the modified drilling equipment and the bore wall. By design principles, the geometry of the profile modifies the trajectory of flowing lines in the annular passage, at the rotational speed ?, and the variation of geometry for drilling fluid passage, (either in terms of passage area or a combination of channel angles through which drilling fluid is forced to flow). There are two different alterations of flowing line patterns corresponding to the two different zones of the profile, where there is a Hydro mechanical cleaning effect and a hydrodynamic bearing effect. In order to have a better understanding of the effects developed by the profiles, the following will firstly describe the principles of the geometry.

Experimental Studies on the Effect of Mechanical Cleaning Devices on Annular Cuttings Concentration and Applications for Optimizing ERD Systems

“…For instance, the use of downhole mechanical hole cleaning device is a relatively recent drilling innovation. Limited studies (Boulet et al 2000;Sapru 2001;Qureshi 2004;Sagheer 2009) have been carried out to evaluate the performance of these devices. Results of these studies showed that the bed height close to the tools is reduced significantly while the bed remains very thick far from the tool zone.…”

“…One of the possible explanations for this is that the turbulence created at the tool gradually diminishes due to viscous dissipation as the fluid flows away from the tool, resulting in redeposition of the cuttings particles on the low-side of the wellbore. Boulet et al (2000) suggested that placement of these tools should be as near as possible to the bottom hole assembly where optimized mechanical behavior of the drillstring and hole cleaning are of the utmost importance. Sapru (2001) conducted bed erosion studies to evaluate the performance of the first generation Hydroclean tools.…”

Important Aspects Related to the Influence of Water Depth on ERW

“…Tests have proven that changing the external profiles of drilling equipments helped to reduce friction and to improve hole cleaning [11]. Tests have proven that changing the external profiles of drilling equipments helped to reduce friction and to improve hole cleaning [11].…”

Computational Fluid Dynamics (CFD) as a Tool to Study Cutting Transport in Wellbores

“…The use of a CFD model is proven to be a successful tool in many areas of fluid flow 15,16,17,18 . More applications of CFD exist in the design and manufacture of drill bits and the related bit hydraulics 19,20,21,22 .…”