Abstract: Example systems, devices, and methods are described for evaluating the relative leak safety of threaded connections in well tubulars. The method includes evaluating leak risk using a quadratic leak criterion, which is a function of the effective pressure (Pe) and includes three constants: a first constant called the leak path factor (?), a thread modulus (?), and a makeup leak resistance (?). The method in some implementations includes identifying at least three test cases with different ?p expected to leak under certain conditions. The method includes fitting a quadratic expression to a subset of values associated with the leaking test cases, in which the resulting quadratic expression includes values for the three constants.

Abstract: Described are systems and methods for evaluating the leak safety of threaded connections in well tubulars. A method, for example, includes assessing leak risk according to a Leak Criterion with Thread Shear. The Leak Criterion with Thread Shear is a function of the conditions relative to a pin-box interface radius and includes two constants: a Thread Modulus (alpha) and a Makeup Leak Resistance (beta). The leak risk is evaluated at the pin-box interface and is a function of differential pressure, effective stress, and shear stress. Lab tests conducted under known conditions are described for calculating the constants, alpha and beta, which are independent of extrinsic states or conditions.

Abstract: A triaxial connection leak criterion for assessing and optimizing threaded connections in well tubulars, together with an associated leak safety factor for use in tubular design, is described. The triaxial leak criterion introduces the dependence of leak on hydrostatic pressure and on two constants associated with the connection: a Thread Modulus and a Makeup Leak Resistance. These two constants represent inherent properties of a particular threaded connection, independent of external conditions. Simple lab tests are described for determining the two connection constants, without expensive qualification testing or finite-element analysis. Graphical tools based on the triaxial leak criterion include a leak line and a leak circle for visually assessing the leak risk associated with any of a variety of load cases.