Hardbanding for Drilling Unconsolidated Sand Reservoirs

Abstract

Abstract Hardbanding materials are used to protect tool joint drillpipe against wearin drilling operations. Hardbanding shall resist wear in openhole conditions with a minimum damage to upper casing. Laying down drillpipe for hardbanding repair can significantly increase rig time and tubular costs. All hardbanding products applied for Sincor were wearing out completely after drilling 15,000ft in 50 hours in the reservoir. It was necessary to search for new hardbanding alternatives with an extended lifetime. A field evaluation program was designed to compare wear resistance of different commercial hardbanding materials and toevaluate new techniques for welding tungsten carbide pellets with alloyingwires and for testing of tungsten carbide spheres being laser applied. Hardbanding products were selected upon analysis of wear mechanisms occurring in drillpipe while drilling horizontal wells in Sincor. Wear resistance was monitored in terms of cumulative drilled footage until gauging complete wear ofhardbanding on tooljoints. One of the newly developed hardbanding products wasfinally selected as the best option after considering its superior wear resistance, minimum expected casing damage, and moderate cost. This is thefirst reported successful application of tungsten carbide pellets welded withina hard matrix provided by an alloy wire for hardbanding purposes. Introduction Wear of drillpipe is an important issue for drilling operations in Sincorarea. Wear increases operational cost due to repair of components, rig time tochange out worn down components, and lost of valuable tools. Wear of components has been reported in the tool joint drillpipes since start of operations.Hardbanding and repair cost for a 5,000-ft string can reach up to US$ 150,000 over the string lifetime. With this amount of money and time invested in wear control, high consideration was given to develop material specifications for requesting wear resistant materials. Other solutions implemented in Sincor toreduce drillstring wear are the following:Use of down-hole tools, i.e. Hydroclean drillpipe, for better hole cleaning and a consequently reduction of the backreaming while drilling horizontal sections.Optimization of drilling practices such as mud circulation, use of Hi-Vispills, and backreaming parameters.Use of mud additives, i.e. Ecolane solvent, and heating the mud to reducedrillstring friction.Use of several types of hardbanding materials. This work is aimed to find the most appropriated hardbanding material forprotecting drillpipes in openhole conditions. Minimum casing wear and environmental pollution due to chromium discharge within the drilling fluidswere identified as special concerns. Background Sincor is an operating oil company created in 1997 and it is comprised by Total Venezuela S.A., PDVSA Sincor S.A., and Statoil Sincor A.S. The company started operations in 1998 to exploit the Zuata reservoir located in the Orinoco Belt in Southeastern Venezuela. Reservoir is characterized by an 8-°APIheavy crude oil in unconsolidated sand with extensive shale bedding. Wells are drilled in clusters to minimize environmental impact. Each cluster has an average of 12 extended reach wells having an average horizontal section of 4,450-ft in length. Frequent backreaming is required for hole cleaning purposes. This combination of unconsolidated sand and repeated backreaming as depicted in Figure 1, are the primary causes for wear of drillstring components. Drillpipe is laid down when tooljoint outside diameter is lower than 6–3/8".