Wells – Packers or plugs – Flow stopping type; e.g. – plug
Reexamination Certificate
2002-04-03
2004-04-06
Walker, Zakiya (Department: 3672)
Wells
Packers or plugs
Flow stopping type; e.g., plug
C166S135000
Reexamination Certificate
active
06715543
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a mixture of particulate matter to hinder/reduce migration of formation fluids in wells, primarily in connection with plugging of wells related to exploitation of hydrocarbons. Formation fluids encompass both liquids and gases in the sub-terrain.
BACKGROUND OF THE INVENTION
Plugging of wells is on the most part carried out by removing the production tubing, upper part of well casings and other superfluous well equipment to the extent that this is possible and necessary. Simultaneously with or prior to the plugging, one or several mechanical plugs are placed in the well, eventually combined with one or several cement plugs. The plugs are commonly placed within a few well intervals, and these represent only a small fraction of the total volume in the well. Similarly, for example related to production, it may be required to perform zone isolation in the well by plugging. The plugging is carried out to hinder eventual fluids in the formations, including hydrocarbons, from leaking to the surface or eventually to another formation in the well, where such leaks would create unwanted and eventual dangerous situations.
The conventional technique for plugging of wells usually requires much work and time and is therefore rather expensive, especially for offshore wells. Much of the work is related to preparations before the plugging operation, such as among others cutting and removal of downhole casings and production tubing(s). The quality of these preparatory works have great impact on how efficiently one manages to place mechanical and/or cement plugs, and on how well the plugs keep a tight seal afterwards. After the placement in the well the metal in the mechanical plugs and in the casings remaining in the well are subjected to corrosion. This will, in the foreseeable future reduce the thickness of the metal by corrosion, eventually they crack under the prevailing physical loads and leakage will occur. Eventual displacements in the Earth's crust can also damage mechanical plugs and cement plugs and make them deform and eventually become fractured. These plugs lack the ability to conform to changes in their environments and will therefore not maintain their function to hinder flow.
An article in the Norwegian Petroleum Directorate's (NPD) magazine ‘Sokkelspeilet’, No. 2, 1999, pp. 12-13, speaks about the risk for well leaks resulting from Earth crust displacements, alluded to above, and where the NPD's concern is to bring forward a method for well plugging that shall have a sufficient durability that in principle is the perspective of eternity.
Although NPD in principle wants the perspective of eternity for the durability of well securing, it is in practice reasonable to assume that well plugs are never absolutely tight for all times. Another practical question concerns what may be viewed as being sufficient well securing.
The purpose of the present invention is to make available a simple and less expensive method for hindering/reducing unwanted migration of formation fluids in wells, primarily in connection with plugging of wells related to the exploitation of hydrocarbons. The invention also aims at making available a more flexible and durable plugging of such wells.
SUMMARY OF THE INVENTION
The purpose is, as described in the characteristic in the present independent and dependent patent claim, realised by preferably applying a poorly sorted mass of naturally occurring and/or synthetic produce of granulated material, eventually like material suspended in a suitable carry fluid, to be placed suitably in the well, eventually also around remaining casings in the well, production tubing, eventually other equipment left in the well, in the entire or portions of the well.
The principle behind the method is known from natural sedimentological processes, and is applied in construction activities, among others for building of the core of dams and dikes. The novelty is that the principle is carried further in the form of a new method whereby a defined mass of particulate matter constitutes the main, preferred material for plugging of wells. The application of the method requires acceptance that a packed particulate matter with low permeability can form a sufficiently impermeable well plug. The mass can for example consist of a poorly sorted mixture of granule, sand, silt and clay. Sorting is among others, a measure of the degree of variability, or width of variation of the different particle sizes in the aggregate mass. The notion of sorting also expresses the distribution of these particle sizes in the aggregate, that yields a statistical description by means of a cumulative distribution function.
A poorly sorted particulate matter consists of particles including several particle sizes. In comparison, a moderately sorted mass consists of a small number of categories of particle sizes, for example medium sand and fine sand, while a well sorted mass includes one category of particle sizes, for example coarse silt. Other examples of particle size categories are very coarse sand (particle diameter 1-2 mm), coarse sand (particle size diameter 0.5-1 mm), very find sand (particle-diameter 0.0625-0.125 mm), fine silt (particle diameter 0.008-0.016 mm), and so forth. These are examples from the so-called Udden-Wentworth scale of particle sizes.
In statistical terms, each particle size category is often expressed by a variation width given as &phgr;-values, where
&phgr;=−log
2
d
(
d
=average particle diameter)
As examples, fine silt has &phgr;-values between 6 and 7 and medium silt has &phgr;-values between 5 and 6. The accompanying scale of particle sizes is known as the Krumbein phi (&phgr;) scale. The distribution of particle sizes in the mass is commonly given by the variation width (in &phgr;-values) that include approximately ⅔ of all the particles in the mass. Statistically this variation width equals two times the standard deviation. The standard deviation is therefore a commonly accepted measure for the sorting of a sediment or a mass of particulate matter.
Both the Udden-Wentworth scale and the Krumbein &phgr;-scale and is other notions are generally known and applied within among others, geological disciplines. There are also other similar scales and/or terminology that in varying degrees are used within different geographical areas and/or engineering disciplines.
The composition of the mentioned particulate material mass must be adapted to the well conditions and objectives one wishes to accomplish for the individual well. There may also be conditions where the composition of the particulate matter can be varied along the length of the well if this appears to be preferable. The mentioned particulate matter mass replaces, eventually is used in combination with conventional mechanical plugs and/or cement plugs, eventually also in combination with other plug types containing e.g. resin or similar additives.
After placement in the well, the particulate matter should over a large length in the well be such sorted, packed and eventually contain a sufficiently irregular form, such that appreciable migration of formation fluid is hindered. Alternatively, the same effect can be achieved by placement of a homogenous and fine-grained particulate matter, such as silt and/or clay in the well. This lastly named alternative however appears impractical since the placement of such a mass would be far more time consuming, and the fine grains require a long time to sediment from the fluidised mass. The mixed in fluid, a so-called carry fluid, must also have viscosity, specific gravity and/or other physical/chemical properties designed for the/those specific objectives one wants to achieve.
The low permeability of the particulate matter results in that a fluid front will move slowly through the mass. The velocity of the fluid front through the particulate material is controlled by adapting the composition of particle sizes and the length of the particulate material plug(s) according to the properties of the migrating fl
Sandaband, Inc.
Walker Zakiya
LandOfFree
Particulate matter plug for plugging a well does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Particulate matter plug for plugging a well, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Particulate matter plug for plugging a well will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3213313