Well classification
Mnemonic Lahee classification Description
NFW New Field Wildcat An NFW well is located at a considerable distance beyond the limits of known pools and is outside the boundaries of existing fields. The well is drilled in an area where hydrocarbons have not yet been discovered. The geological risk of this type of well is very high: in the absence of the discovery of a new pool, the well would be deemed successful. Samples are collected from base of surface casing to total depth.
NPW New Pool Wildcat The objective of an NPW well is the discovery of a new pool(s) in all zones that the well encounters. The well is located in an already discovered field. The geological risk of this type of well is very high: in the absence of the discovery of a new pool, the well would be deemed unsuccessful. In circumstances where the well is in relatively close proximity to the limits of a known pool(s), the NPW classification must be based on technical data suggesting that a new pool will be encountered. A well drilled within or in close proximity to the limits of a known pool(s) but terminating shallower than the known pool(s) is normally classified as NPW, except in the case where pre-existing wells in close proximity to the well have logs and/or tests that strongly suggest the existence of shallower pools to be penetrated by the well. Samples are collected from 30 m above shallowest potential hydrocarbon bearing horizon to total depth.
DPT Deeper Pool Test A DPT well is located within or in close proximity to a known pool(s) and is drilled with the objective of exploring for new, undiscovered pool(s) below the deepest of the known pool(s). Only the interval below the deepest of the known pool(s) is exploratory and carries a high geological risk. The remaining metreage in a DPT is development, with low geological risk. In circumstances where the exploratory portion of the well is in relatively close proximity to the limits of a known pool(s), the DPT classification must be based on technical data suggesting that a new pool will be encountered. Drill cuttings samples are collected from 30 m above the first potential hydrocarbon bearing horizon to be encountered after the well drills through the deepest designated pool to total depth.
OUT Outpost An OUT well is drilled with the intention of extending a known pool by a considerable distance. A well in proximity to a known pool but whose outcome is uncertain because of geological complexities might also be classified as OUT. There would be some geological risk associated with drilling an OUT well. Drill cuttings samples are collected from 30 m above the first potential hydrocarbon bearing horizon to be encountered after the well drills through the deepest designated pool to total depth.
DEV Development The objective of a DEV well is to further exploit or extend a known pool(s). The well may be inside of the established limits of the pool or in close proximity to the edge of the pool(s). The DEV classification should be used even if the well is drilled slightly deeper than the target pool, especially where the deeper strata to be penetrated have no hydrocarbon-bearing potential. The geological risk of this type of well is low. Wells licensed with a well type of production and substance of bitumen are DEV. No drill cutting samples are required.
REN Re-entry A REN classification is assigned to a well that re-enters an existing wellbore for the purpose of recompleting the well as a producer or service well with no new strata being drilled. If new strata are to be drilled (e.g., by deepening, whipstock, or sidetracks), the well is assigned the appropriate Lahee classification. No drill cutting samples are required.
DSW Development Service Well A DSW well is drilled to introduce fluids into a formation or observe the performance of a reservoir. Water injection, steam injection, and observation wells are examples of DSW wells. No drill cutting samples are required.
OV Evaluation Oil Sands An OV well is drilled in an oil sands area to evaluate the oil sands and is not intended to produce hydrocarbons. No drill cutting samples are required.
TH Test Hole A TH well is drilled for geological and geophysical stratigraphic evaluation purposes and is not intended to produce or expected to encounter hydrocarbons. No drill cutting samples are required.
EX Experimental An EX well is part of an experimental scheme. Samples are collected from 30 m above shallowest potential hydrocarbon bearing horizon to total depth.
OTH Other A well drilled for water production, brine production, gas storage, water disposal, or any other purpose not covered by other Lahee classifications is classified as OTH. No drill cutting samples are required.

This classification of exploratory wells was established by Frederic H. Lahee in 1944, and has been used since then by AAPG-CSD and API. It was widely adopted throughout North-America and is used with a few additions at well licensing procedure in Canada's provinces and territories.

Mnemonic initial confidential status Description
C CONFIDENTIAL NFW,NPW,TH,OV,EX wells are innitially confidential.
C CONFIDENTIAL OUT, DPT, DEV, DSW, REN wells are innitially confidential if all zones penetrated by the well are outside the limits of a designated pool or inside the boundaries of an existing confidential pool.
NC NONCONFIDENTIAL OUT, DPT, DEV, DSW, REN wells are innitially non-confidential if the well terminates in or just below a designated nonconfidential pool. If the well type and substance are production of crude bitumen in an oil sands area, the well is also nonconfidential.
CB CONFIDENTIAL BELOW OUT, DPT, DEV, DSW, REN wells are innitially non-confidential if one or more up-hole zones penetrated by the well is inside a designated nonconfidential pool. The confidential below formation name is the name of the deepest designated pool the well penetrates.
NC NONCONFIDENTIAL OTH wells are innitially non-confidential.

A confidentiality assignment takes into account all zones to be penetrated by the well. After a well has been drilled, the operator may request a revision to its confidentiality assignment based on the result of drilling.

© March 2011, Chinook Consulting Services

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