Heat Checking/Quench Cracking Tool Joints

Abstract

SPE Members Abstract Tool joints may be heated in service above the critical temperature of steel through the heat of friction. When this steel is quenched by the drilling mud, longitudinal cracks develop. These initially shallow cracks propagate rapidly. In boxes they lead to washouts near the makeup shoulders. In pins, some cases have lead to pin base failures and fishing jobs. This drill string problem has plagued the oilfield for more than 40 years. In spite of this, many experienced drillers are unaware of its existence and have difficulty accepting the facts when they are first presented. Heat checking/quench cracking of tool joints may occur when they are forced against the wall as they are rotated or pulled from the hole. This force or side pulled from the hole. This force or side thrust may result from an intentionally deviated well or from one which developed a severe dogleg. The effects of severe in-hole heating has recently been observed on bottom hole assembly components used with top drive systems. Introduction During the past several years, there has been a noticeable increase in tool joints failures due to in-hole friction heating. Various bottom hole assembly components have also failed due to this phenomena. When users are confronted with phenomena. When users are confronted with the cause of failure the initial reaction is often disbelief. The purpose of this article is to help users and inspectors recognize the problem and to remove the affected members from 'the working drill stem before they result in downhole washouts and/or fishing jobs. THE PHENOMENA/HISTORY Heat checking or friction heating is the result of rapid heating and cooling of the tool joint OD. A pattern of parallel surface cracks are formed perpendicular to the direction of rotation (Figure 1). Metallurgical examination of longitudinal sections taken through joints show variable patterns of heat-affected zones below the patterns of heat-affected zones below the OD surface. Often, these zones extend as much as 1/4" or more below the OD surface (Figure 2). The micro-structure in these zones indicate definitely that the material has been heated above the critical temperature of 1450 deg. F. The hardness in these zones will often vary from higher than the original material hardness to lower than the original material hardness. These zones often overlap each other as shown in Figure 2. This indicates that the joint was subjected to irregular heating and quenching cycles during the drilling operation. Heating above the critical temperature results from the friction developed between the tool joint OD and the casing, formation, or some other object that the tool joint may rub against. Drilling fluid provides the environment for the rapid provides the environment for the rapid cooling. P. 51