The first well which reaches the oil is the "discovery".

That quantity of petroleum which is estimated, on a given date, to be contained in known accumulations, plus those quantities already produced therefrom. Discovered Petroleum-initially-in-place may be subdivided into Commercial and Sub-commercial categories, with the estimated potentially recoverable portion being classified as Reserves and Contingent Resources respectively (SPE).

The term applied to a petroleum accumulation/reservoir whose existence has been determined by its actual penetration by a well, which has also clearly demonstrated the existence of moveable petroleum by flow to the surface or at least some recovery of a sample of petroleum. Log and/or core data may suffice for proof of existence of moveable petroleum if an analogous reservoir is available for comparison.

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A change in the formation that may have been caused by ancient erosional forces. Accounts for variances in formation tops in near-by offset wells in a formation with no pay inclination.

A formation that comes apart or disaggregates or separation of grains.

Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content.

Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content.

A measurement of the well path that records the inclination and azimuth of the wellbore using a compass or other device.

A rock with a higher permeability along a given plane, usually created by natural fracture development, water flow that leaches the pores, depositional environment or localized reworking of the sediments.