Wells – Processes – Placing fluid into the formation
Reexamination Certificate
1999-01-12
2001-09-11
Shackelford, H. (Department: 3672)
Wells
Processes
Placing fluid into the formation
C166S307000, C166S308400, C166S313000
Reexamination Certificate
active
06286600
ABSTRACT:
BACKGROUND OF THE INVENTION
Commonly, in the oil industry, it is necessary to treat wells with materials such as stimulation fluids. In certain stimulation processes, it is necessary for the fluids to be under enough pressure that they penetrate the rock surrounding the well, and that the fluids be dispersed at specific locations desired by the operator along the length of the well. This becomes especially necessary with horizontal wells which can have very long uncased portions requiring stimulation.
Traditionally, in the oil industry, two methods have been used to distribute treatment or stimulation materials into an uncased well. One method is the “bullhead” treatment method in which a jointed tubing is run to the bottom of the vertical or cased section of the well, and stimulation materials are pumped through the tubing, out of its bottom end, into the uncased portion of the well. This method has been successful in creating high enough pressures such that rock penetration, or “matrix acidizing” can be achieved, or the rock may be parted in a fracture treatment. However, studies have shown that this method offers very poor distribution of stimulation materials throughout the well, and does not allow the operator to determine where in the formation the stimulation materials are distributed.
Another method that has been used is the coiled tubing method, wherein a thin coiled tubing is run down the length of the well as stimulation materials are pumped through the coiled tubing. This method offers very good distribution of stimulation materials, however the coiled tubing method does not provide enough pressure such that the stimulation materials are able to adequately penetrate the matrix of, or fracture, the rock surrounding the well.
Another well stimulation system popular in the early 1980's was the “limited entry” system. This method was used exclusively with vertical, cased wells and involved perforating the casing at specific locations in the well. After a vertical well was completed with casing cemented in place, the casing was perforated in specific locations along its length and stimulation materials were pumped into the well. Thus, an operator could stimulate specific perforated portions of the vertical cased well. This method, however, did not allow any variance of the locations to be treated at a later time. The casing perforations were permanently in place, and if further locations were desired to be treated, the original perforations could not be removed without losing the pathway to the original treatment. The stimulated areas could only be added, and not varied. Thus, repeated stimulation of the same cased, vertical well in different locations resulted in a reduction of the desired distribution.
In uncased wells, the limited entry method is not available, especially when the uncased portion of the well is deviated. According to J. A. Short, author of
Introduction to Directional and Horizontal Drilling
, p. 215 (1993), fracturing and acidizing stimulation techniques are uncommon in horizontal open hole completions because “it is difficult to determine the amount and location where treating fluid enters the formation.” Thus, for the foregoing reasons, there is a need for an improved stimulation method for use with deviated, uncased wells, providing the operator with a sufficient ability to distribute stimulation materials at particular locations in the formation while also providing adequate pressure such that stimulation materials can penetrate the matrix of or fracture, the rock if necessary.
SUMMARY OF THE INVENTION
The present invention is directed to a process for providing stimulation or other materials, such as acidizing fluid, to the uncased portion of a well while providing a specifically desired distribution of the material along the well's length, as well as adequate pressure such that the stimulation materials can penetrate the matrix of, or even fracture, the rock if necessary. The specific distribution locations may then be easily varied and/or used with other wells. One exemplary method involves taking a normal jointed tubing string and inserting ported subs, which are portions of tubing with holes along their length, at calculated intervals along the tubing string's length, depending on what area of the formation is desired to be treated. These ported subs may be joints of typical production tubing, or other specially manufactured joints of tubing, which have openings along their length sufficient to release stimulation materials. Because production tubing may be used, stimulation materials may be pumped into the well at a sufficient pressure such that the rock can be penetrated. Also, the distribution of holes along the tubing's length provides an opportunity for the stimulation materials to be deposited into the well at calculated points along its length. This provides a specifically desired distribution of stimulation materials along the length of the well. The tubing can then be removed and the location of the ported subs changed such that a different desired distribution can be achieved with the same or different well.
It is preferred that in this method the bottom end of the jointed tubing string be plugged for maximum effectiveness. Also, if the well to be treated is one with a number of laterals originating from the same primary drilling hole, an inflatable packer can be placed at the top of the lateral being treated, after its kick off point from the central bore hole, such that the stimulation materials do not overflow into other laterals, and such that pressure is maintained in the lateral being treated.
REFERENCES:
patent: 4951751 (1990-08-01), Jennings, Jr.
patent: 5117912 (1992-06-01), Young
patent: 5363919 (1994-11-01), Jennings, Jr.
patent: 5743334 (1998-04-01), Nelson
patent: 5765642 (1998-06-01), Surjaatmadja
patent: 5899274 (1999-05-01), Frauenfeld et al.
J.A. Short, Introduction to Directional and Horizontal Drilling, 1993, pp. 214-221.
Crawley Cal
Ellis Patrick D.
Hall Scott D.
Kniffin Glen M.
Sullivan Danny F.
Howrey Simon Arnold & White
Reinisch Morris N.
Shackelford H.
Texaco Inc.
LandOfFree
Ported sub treatment system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ported sub treatment system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ported sub treatment system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2484095