05.07.2009
The pressure of the flowing well measured at the intake point in the borehole.
Floating production systems are essentially semisubmersible drilling rigs, except that they contain petroleum production equipment, as well as drilling equipment. Ships can also be used as floating production systems. The platforms can be kept in place through large, heavy anchors, or through the dynamic positioning system used by drillships. With a floating production system, once the drilling has been completed, the wellhead is actually attached to the seafloor, instead of up on the platform. The extracted petroleum is transported via risers from this wellhead to the production facilities on the semisubmersible platform. These production systems can operate in water depths of up to 6,000 feet. Choosing the right FPS depends on the water depth, hull motions, and the type of riser system desired. The riser system and the motions of the FPS hull are key. For tensioned risers, the wellhead has to be accessible from directly below the FPS. Once below the mudline, wells can divert in different directions to access particular reservoirs, which could be several miles away. However, if the reservoir is fragmented, spread over a large area, or has tiebacks, a steel catenary riser (SCR) is used. Basically, an SCR is a pipeline that’s been picked up off the floor and hung off the FPS. The riser is the section of the pipeline from the mudline up to the FPS. To use top tensioned risers (dry trees) or SCRs, a spar or tension leg platform (TLP) is traditionally used because of their small in-place motions. A spar has a deep draft of 550 ft, and a TLP’s motions are constrained by tendons designed to withstand tensions induced by wave forces. A conventional semisubmersible is not designed to support dry tree risers. Its shallow draft of 60-80 ft creates motions too large to use top tension risers or SCRs. TLPs typically work in water depths less than 5,000 ft because of their tendon design. Therefore, from 5,000-10,000 ft, the only top tension riser choice is a spar. The one disadvantage to a spar is its delivery method. It has to be towed out to its final location on its side, up right, and placed on its moorings. The topsides then have to be lifted by modules and commissioning is done offshore, which is expensive and risky. Topsides for TLPs and semisubmersibles are lifted quayside, and the entire FPS is towed to its location and installed. Furthermore, a semisubmersible and TLP have larger deck areas than a spar. A spar is limited to its diameter, so operators end up stacking the decks. A spar could have three decks as opposed to one or two on a semisubmersible or TLP. Ideally one would like to have the functionality of a semisubmersible, but the motions of a spar.
Formation damage is a problem that can occur during the various phases of oil and gas recovery from subsurface reservoirs including production, drilling, hydraulic fracturing and workover operations. Formation damage assessment, control and remediation are among the most important issues to be resolved for efficient exploitation of hydrocarbons. Formation damage indicators include permeability impairment, skin damage and decrease well performance
Share of the total firm capacity that the terminal operator has agreed on with a shipper in a terminal access contract. The capacity is deemed to be booked as soon as the reservation request has been accepted by the terminal operator. The price of the firm capacity subscribed is the access tariff in force. A minimum payment commitment is associated with this capacity, in accordance with the tariff conditions in force
An FPSO system is an offshore production facility that is typically ship-shaped and stores crude oil in tanks located in the hull of the vessel. The crude oil is periodically offloaded to shuttle tankers or ocean-going barges for transport to shore. FPSO’s may be used as production facilities to develop marginal oil fields or fields in deepwater areas remote from the existing pipeline infrastructure.
It is a moored or dynamic positioned floating structure.
Retrieving objects from the borehole, such as a broken drillstring, or tools
In time the flowing tubing pressure of a gas well may decline and further compression may be needed
All shippers need to balance their gas shipments through the pipeline system, namely to maintain their input and withdrawal of natural gas below a specific tolerance level on both a daily and monthly basis. Shippers can balance their system by buying or selling gas in the highly liquid on system market where the price of natural gas determines the cost of maintaining their balance. But shippers do not always maintain their daily balance and the whole pipeline system may become unbalanced if the sum of individual imbalances exceeds a certain tolerance level. The pipeline operator must then inject or withdraw natural gas to restore the balance. The value of the natural gas in these transactions is not reflected in the on-system price. To facilitate the pricing of this gas the flexibility mechanism was introduced in 1996 in the UK. The flexibility mechanism allows market based determination of the value of the natural gas needed to restore the balance in the pipeline system. This gas is traded in an auction and interested bidders post their bids specifying volumes and the price at which they want to buy or sell. The pipeline operator buys gas if it expects that injections into the system will be less than withdrawals and vice versa.
Fluid (such as gas, oil, or water) that exists in a subsurface formation
A term used in the sale of gas to denote an absolute obligation on the seller to deliver gas and the same obligation on the buyer to accept delivery of an agreed upon quantity of natural gas