PCD Technology Advances Sidetracking Capabilities

Abstract

Innovative materials technology advances sidetracking capabilities and offers a cost-effective approach to creating multiple laterals from the same mother bore. The key component to this sidetracking system is a mill designed with polycrystalline diamond (PCD) inserts. Current technology dictates that sidetrack milling be performed with mills dressed with crushed or pre-formed tungsten carbide that is manually applied. Regardless of technology, the success of the sidetrack is dependent upon on the skill and experience of the welder to properly dress the mill. The PCD mill eliminates the dressing process and the related performance uncertainties. This paper discusses how PCD cutters, which are commonly used in drilling, were modified and applied to a casing-sidetracking mnill. The mill design capitalizes on their ability to effectively and swiftly cut a window in the casing and drill a rat hole in formations with compressive strengths of up to 40,000 psi. The benefits of such a mill are:using the same cutting element for both steel and hard formations,substantial cost savings when constructing multiple laterals from the same mother bore,increased consistency in mill manufacture,reliable milling performance andimproved efficiency in the sidetracking operation. This paper profiles the development and testing from concept to a field-proven tool. The paper details:laboratory-milling tests that identify the best material for cutting steels,Oklahoma field tests in 9–5/8 in. casing to verify the feasibility of PCD casing milling and formation drilling,West Texas and Colombia field runs in operators' 7 and 9–5/8 in. casing to mill a window and drill hard formations. Additionally, the paper will elaborate on the future potential of integrating this technology to a directional drilling assembly to drill laterals with the same equipment and preferably in the same trip for short laterals. Introduction The individual performance of mills used to cut a casing window and sidetracking a well can differ widely. This is due to varying downhole conditions, operating parameters and applications.1 Properly managed quality and process controls, instituted for the manufacturing of milling tools, are essential for consistent performance. Current technology dictates that casing sidetracking mills are dressed with crushed tungsten carbide and/or pre-formed tungsten carbide. It is this cutter dressing that is the cutting structure responsible for removing steel and formation. The dressing must be able to withstand the diverse grades and weights of casing and the varying hardness and abrasiveness of the rat hole formations. The dressing process requirements for successful manual application of the crushed and pre-formed tungsten carbide are very demanding. The quality of the process is dependent upon the skill of the applicator or welder. The consistency of the application is paramount to the success of the mill. Sidetracking mills must adhere to critical design criteria. For this reason, elimination of the often difficult and usually inconsistent dressing process and potential performance uncertainties is preferred. Sidetracking Synergy In light of the irregularities that have been associated with conventional sidetracking mills, the concept of using PCD inserts in place of conventional cutting structures for casing sidetracking was developed. Utilizing PCD inserts as the cutting structure could potentially increase consistency in product manufacturing and performance. The cylindrical PCD cutting elements would be precisely placed in the cutting structure of the PCD Mills. The PCD Mill could deliver a much more reliable milling performance and overall improved efficiency in the sidetracking operation, because it would no longer have to rely on the labor-intensive process of correctly or specifically applying crushed and/or pre-formed tungsten carbide.