05.07.2009

At times during the drilling of wells in the earth, particularly deeper wells, the drill string cannot be retrieved from the wellbore, i.e., it becomes stuck in the wellbore. The stuck-drill string problem has been widely studied, and it has generally been concluded that the more common mechanisms which can cause the drill string to become stuck include: the hole becomes unstable and collapses around the drill string; a “key seat” of the width of the drill pipe diameter forms in the wellbore wall, such that larger diameter members of the drill string cannot be pulled through; segments of the drill string are held against the wellbore wall by excess hydrostatic pressure of the drilling fluid; and, solids build-up of cuttings in the wellbore around the drill string causes sticking. Those skilled in the art of drilling can often determine which mechanism caused the drill string to become stuck, based upon a review of observations before and after the sticking occurred.

A trap in reservoir rock which has been formed by the deformation (folding or faulting) of the rock layer. There are three basic forms of a structural trap in petroleum geology: anticline trap, fault trap and salt dome trap all of which result in barriers which form traps

SSVs are the fleet of offshore support vessels that provide what is known as ‘good prospect of rescue and recovery’ for the personnel onboard offshore installations platforms whilst carrying out their work on site.

Stored natural gas plays a vital role in ensuring that any excess supply delivered during the offpeak months is available to meet the increased demand of the peak months. Natural gas in storage also serves as insurance against any unforeseen accidents, natural disasters, or other occurrences that may affect the production or delivery of natural gas. Natural gas storage plays a vital role in maintaining the reliability of supply needed to meet the demands of consumers. See also Base Load vs. Peak Load Storage >

Refers to rock formations lying beneath long, horizontal layers of salt. These rock formations may contain hydrocarbons. Oil and gas exploration in which prospects exist below salt layers

Arrangement of piping designed to catch a slug of liquid in the gas pipeline to separate it from the gas, or equipment for the purification of water.

In a natural gas pipeline, the liquids flow along the bottom of the pipleines (except in steeply inclined and vertical lines) with the gas flowing over the top “sweeping” the liquid along the pipelines. At lower gas flowrates, the amount of liquid held up in the flowlines tends to build up as the gas velocity is insufficient to “sweep” the liquids up the inclines and out of the flowlines. In addition, steep rises and falls in hold up rate can be caused by the undulations in the pipeline. In order to properly estimate all of the above, accurate bathymetric information needs to be available.

At very low flow rates, the amount of liquid held up in the low parts of the flowlines can build up to the point that a liquid “blockage” occurs. This liquid blockage is often referred to as a slug. The formation of slugs can result in instabilities in flowline operation leading to unsteady flows to the inlet of the receiving facility at the end of the flowline. Unsteady flow of gas and liquid to the terminal facility can result in poor operation of the facility. In order to help smooth the flow of fluids into the facility, a “Slug Catcher” may be installed, which provides a storage volume for liquids produced from the pipeline system. This volume allows the flow to the downstream plant to be smoothed out, helping a steady flow to be maintained.

Another reason for provision of a slug catcher is to manage liquids produced as the flowrate through the pipeline system varies. In general, an increase in gas rate is generally accompanied by an increase in liquid rate at the terminal both due to the increased liquid volumes associated with the additional gas, but also due to the production of the difference in liquid holdup between the lower and higher gas rate.

Spot market is a real time market, usually a matter of days or weeks in the natural gas market. In many countries gas spot prices are reported by pipelines. 10-12% of world LNG is traded on spot deals. Spot market participants have the flexibility to choose the time and quantity of supply based on current needs and price. Many consumers prefer a flexibility that allows them a mixture of long term and short term contracts to enable them to minimize supply and price risks in both the long and short term. Spot prices tend to be volatile responding to changes in supply and demand such as weather, available pipeline capacity

A means of reducing the cost of a well by drilling a smaller-diameter hole than is customary for the depth and the types of formations to be drilled. A slim hole permits the scaling down of all phases of the drilling and completion operations; i.e., smaller bits, less powerful and smaller rigs