Abstract: A shock de-coupler for use with a perforating string can include perforating string connectors at opposite ends of the de-coupler, a longitudinal axis extending between the connectors, and a biasing device which resists displacement of one connector relative to the other connector in both opposite directions along the longitudinal axis, whereby the first connector is biased toward a predetermined position relative to the second connector. A perforating string can include a shock de-coupler interconnected longitudinally between components of the perforating string, with the shock de-coupler variably resisting displacement of one component away from a predetermined position relative to the other component in each longitudinal direction, and in which a compliance of the shock de-coupler substantially decreases in response to displacement of the first component a predetermined distance away from the predetermined position relative to the second component.

Abstract: A bending shock de-coupler for use with a perforating string can include perforating string connectors at opposite ends of the de-coupler. A bending compliance of the de-coupler may substantially increase between the connectors. A well system can include a perforating string including at least one perforating gun and multiple bending shock de-couplers, each of the de-couplers having a bending compliance, and at least two of the bending compliances being different from each other. A perforating string can include a bending shock de-coupler interconnected longitudinally between two components of the perforating string. A bending compliance of the bending shock de-coupler may substantially decrease in response to angular displacement of one of the components a predetermined amount relative to the other component.

Abstract: A shock sensing tool for use with well perforating can include a generally tubular structure which is fluid pressure balanced, at least one strain sensor which senses strain in the structure, and a pressure sensor which senses pressure external to the structure. A well system can include a perforating string including multiple perforating guns and at least one shock sensing tool, with the shock sensing tool being interconnected in the perforating string between one of the perforating guns and at least one of: a) another of the perforating guns, and b) a firing head.

Abstract: A method of mitigating perforating effects produced by well perforating can include causing a shock model to predict perforating effects for a proposed perforating string, optimizing a compliance curve of at least one proposed coupler, thereby mitigating the perforating effects for the proposed perforating string, and providing at least one actual coupler having substantially the same compliance curve as the proposed coupler. A well system can comprise a perforating string including at least one perforating gun and multiple couplers, each of the couplers having a compliance curve, and at least two of the compliance curves being different from each other. A method of mitigating perforating effects produced by well perforating can include interconnecting multiple couplers spaced apart in a perforating string, each of the couplers having a compliance curve, and selecting the compliance curves based on predictions by a shock model of shock generated by the perforating string.

Abstract: A shock de-coupler for use with a perforating string can include perforating string connectors at opposite ends of the de-coupler, a longitudinal axis extending between the connectors, and a biasing device which resists displacement of one connector relative to the other connector in both opposite directions along the longitudinal axis, whereby the first connector is biased toward a predetermined position relative to the second connector. A perforating string can include a shock de-coupler interconnected longitudinally between components of the perforating string, with the shock de-coupler variably resisting displacement of one component away from a predetermined position relative to the other component in each longitudinal direction, and in which a compliance of the shock de-coupler substantially decreases in response to displacement of the first component a predetermined distance away from the predetermined position relative to the second component.

Abstract: A method of utilizing a shock model for prediction of perforating effects can include recording measurements of the perforating effects on an actual perforating string in a wellbore, adjusting the shock model so that predictions of the perforating effects output by the shock model substantially match the measurements of the perforating effects, and causing the adjusted shock model to predict the perforating effects for a proposed perforating string. A method of predicting perforating effects on a perforating string in a wellbore can include inputting a three dimensional well model and a three dimensional model of the perforating string into a shock model, and causing the shock model to predict the perforating effects on the perforating string.

Abstract: A controller in an optical switch providing optical coupling of an optical signal between a source port and a target port employs, in at least one axis, gradient control using a feedback loop that compensates for alignment error between a source port and a target port in an optical switch. In at least one other axis, the controller generates a control input according to a control law that results in variable attenuation of optical coupling between the source port and the target port in the optical switch. A dither signal may be applied to the control input in the at least one other axis. Amplitude of the applied dither signal may be varied.