Because of the growing scarcity of hydrocarbonaceous fluids, there is a continuous need to find additional hydrocarbonaceous reserves. In order to find these hydrocarbonaceous reserves, it is necessary to explore deeper and into more hostile environments to obtain hydrocarbonaceous fluids. Metals used in oil country tubular goods must therefore encounter more harsher environments than previously known. Thus, oil country tubular goods and other metals similarly used in the exploration and production of hydrocarbonaceous fluids must endure greater pressures, hotter temperatures, greater hanging stresses, and harsher chemical environments than previously enountered.
Much interest has therefore been directed into ways for determining how metals will react in these harsher environments. As is generally known, similar type metals, which bear the same type designation, often vary considerably in their behavior in actual operating conditions. There has been much conjecture as to why these variations occur, particularly when the metals are obtained from the same manufacturer. To remove these vexations, others have taught methods for determining the fatigue and relaxation potentials of metals under stress. One such method is disclosed by Oertle et al. in U.S. Pat. No. 4,179,940 issued Dec. 25, 1979. Via this method crack initiation in metallic structure members subjected to cyclic loading was predicated by sensing metallurgical changes taking place as a result of cyclic loading. Fatigue loading produced a cycle comprising a condition described as fatigue relaxation followed by fatigue intensification. By monitoring this cycle, measured strain for a known applied load would increase or decrease. By monitoring the change in strain load, crack initiation could be predicated as fatigue relaxation became fatigue intensification. In a preferred embodiment, a strain gauge was mounted beneath a patch, which patch excluded ambient atmosphere during monitoring of the structural members.
Therefore, what is needed is a method to predict how a metal will behave in a hostile environment which environment includes exposure to heated chemicals, higher pressures, and physical stresses greater than heretofore encountered.
USPTO Backgrounds
USPTO Backgrounds