Abstract: Methods of detecting and measuring in-situ elastic anisotropy in a subterranean rock formation penetrated by a well bore are provided. The methods basically include exerting pressure on the formation by way of the well bore, and measuring the incremental diametral displacements of the well bore at a location therein adjacent the formation as the pressure on the formation is increased. The magnitudes of the diametral displacements are compared to detect and measure elastic anisotropy in the formation.

Abstract: The present invention comprises a pressure balanced tubular spring slip-joint and jar including a generally tubular outer housing having longitudinal slot means in the wall thereof, and a hammer area of increased wall thickness at one end thereof, within which housing slidably extends a jar mandrel means having first and second longitudinally spaced enlarged diameter anvil areas, at least one fastener tapped into one of those anvil areas, the heads of said fastener protruding into said slot means. Both said housing and said mandrel means possesses axial bores therethrough, which are placed in communication via the bore of a tubular spring within the housing, whereby during extension and contraction of the slip-joint and jar means of the present invention the area within said axial bores and said spring bore is of a constant volume.