Core drill assembly with adjustable total flow area and restricted flow between outer and inner barrel assemblies

Abstract

A core drill assembly with replaceable fluid nozzles permitting effective total flow area adjustment (TFA), substantial optimization of hydraulic force at the cutting face to improve rate of penetration (ROP) and core quality. At least one seal assembly to restrict drilling fluid flow while permitting mutual rotation between the core head ID and the lower shoe is disposed in an annulus defined therebetween.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60 / 800,620, filed May 15, 2006, the entire disclosure of which is incorporated herein by reference.FIELD OF THE INVENTION[0002]Embodiments of the present invention are related to a core drill assembly with adjustable drill fluid total flow area and, more particularly, to a core drill assembly which includes replaceable cutting fluid nozzles and a seal assembly disposed between adjacent portions of the outer barrel assembly and the inner barrel assembly, as well as to methods of coring.BACKGROUND[0003]Current core head designs use a fixed total flow area (TFA) to circulate drilling fluid through the core head, also known as a core bit, during down-hole coring operations. The TFA is a calculated discharge area for the drilling fluid which may include an annulus ID gauge fluid course between the core head ID and the exterior of the lower shoe, carried by the ...

AI Technical Summary

Problems solved by technology

If the hydraulic force is too low, there will be poor cleaning of the cutting structure and cuttings will interfere with the rate of penetration (ROP) in forming the bore hole.

If the hydraulic force is too high, there may be erosion of the bole hole, which can result in a stuck drill string, and the drilling fluid may contaminate the core sample.

However, since the TFA is non-adjustable, the operator cannot optimize the amount of drilling fluid at the drill face 16 of core head 14 and the HSI.

With the non-adjustable TFA of current core head designs, the only variable is the circulation rate of the drilling fluid, and therefore, the HSI cannot be optimized.

In core heads using ID fluid courses only, all of the flow travels through the annulus whereas, when core head face discharge ports are used in combination with the annulus, it is difficult to determi

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