Category: Oil and Gas business

A sedimentary layer of rock cemented together in a manner that greatly hinders the flow of any gas through the rock

Arrangement between parties to a drilling agreement, whereas an investor pays 1/3 of the costs in return for only 1/4 of the equity in the field.

A working shift for drilling crew or other oilfield workers. Some tours are 8 hours; the three daily tours are called daylight, evening (or afternoon), and graveyard (or morning). 12-hour tours may also be used; they are called simply day tour and night tour.

This is gas that is stuck in a very tight formation underground, trapped in unusually impermeable, hard rock, or in a sandstone or limestone formation that is unusually impermeable and non-porous (tight sand).

Tight gas sands is one type of unconventional reservoirs. Typical unconventional reservoirs include also coal bed methane, heavy oil and gas shales. Tight reservoirs contain no natural fractures and cannot be produced economically without hydraulic fracturing. Tight reservoirs are in essence reservoirs with low permeability. It has been coined by some as a reservoir of natural gas with an average permeability of less than 0.1 millidarcies or by others as a reservoir with an average effective gas permeability of less than 0.6 mD. A tight gas reservoir is often defined also as a gas bearing sandstone or carbonate matrix, which may or may not contain natural fractures which exhibits an in situ permeability to gas of less than 0.10 mD. Many ultra tight gas reservoirs may have in situ permeability down to 0.001 mD.

A number of reasons can contribute to making a reservoir tight. Basically, the permeability that determines the ease at which a fluid can flow is a function governed by Darcy’s Law of fluid flow in a porous medium. Effective porosity, viscosity, fluid saturation and the capillary pressure are some of the important parameters that affect the permeability of a reservoir.

Namely when the owner of natural gas infrastructure (such as an LNG regasification terminal) does not have to offer capacity to third parties, which often renders the project more attractive for the investor. This was first ratified in the Hackberry ruling in the USA. The exemption rules are nevertheless complex and include a host of additional stipulations such as possibly having to grant access to unused capacity or having to set aside a portion of the base capacity (i.e. TPA exemption can be granted but possibly only for 80% of the base capacity)

A well which the operator wishes to keep secret, especially the geological information thereof