Wells – Processes – With indicating – testing – measuring or locating
Reexamination Certificate
1999-09-13
2001-10-09
Neuder, William (Department: 3672)
Wells
Processes
With indicating, testing, measuring or locating
C166S055100, C166S297000, C175S004510
Reexamination Certificate
active
06298915
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a method and apparatus for properly orienting a modular downhole tool such as a perforation gun. Specifically, it relates to an apparatus that allows the tool to be positioned with a particular angular orientation.
2. Description of the Related Art
Perforating casing in a wellbore involves lowering a perforating gun or guns into the wellbore, positioning the gun(s) adjacent to the geological zone intended to be perforated, and detonating the perforating gun(s). The geological zone of interest is generally laid down in a horizontal plane. However, geological formation attributes such as porosity and/or permeability may vary around the circumference of the wellbore. A preferred vertical plane may exist within the horizontal plane of the formation for porosity and/or permeability. In such a preferred vertical plane, the porosity and/or permeability of the formation may be more advantageous for producing hydrocarbons from the formation. Therefore, orienting the perforating gun(s) with respect to the preferred vertical plane of the formation would tend to increase the producibility of the well. Other advantages gained from orienting the perforating gun(s) with respect to the direction of the preferred vertical plane might be realized in mechanical fracturing operations, as well as in acidizing operations performed on the formation of interest. By orienting the perforations with the preferred vertical plane, the hydraulic pressure for fracturing and the reactive acid from acidizing are aligned with the best possible porosity and/or permeability vertical plane, which allows each to penetrate deeper into the formation. Also, in a situation where a well is blowing out and a relief well is drilled for diverting the blowout pressure and flow, complete control over the relief well is maintained by perforating into the blowout well from the relief, rather than drilling into the blowout. Oriented perforating provides a means for maximizing the communication between wells.
A problem with current technology is the inability to orient slickline perforating guns along the maximum horizontal stress while simultaneously perforating an entire zone in a given vertical direction in order to lessen the effects of sanding in a newly perforated well.
The perforating gun(s) can be conveyed into the well using either tubing or wireline as a conveyance. By using tubing as the conveyance, the perforating charges within the perforating gun may be oriented at a 180° phase from each other, which enables the well operator to perforate only in the angular orientation of the preferred vertical plane without wasting perforating charges oriented at other directions. This is performed by lowering the perforating gun(s) into the wellbore attached to the tubing, and once the perforating gun is positioned across the formation of interest, a direction survey is performed for finding the orientation of the perforation gun(s) with respect to the preferred vertical plane. Running the perforating gun(s) on tubing requires a special anchoring device on bottom of the stringer or, without anchoring device, firing is limited to a mechanically operated firing head. With an anchoring device the perforation gun(s) can be fired with pressure.
A wireline or slickline unit is normally used for running the direction survey. By using a wireline the operator gets a real time readout of the orientation of the perforating gun at the surface. Once the orientation of the perforating gun(s) is determined, the tubing is rotated a corresponding amount for angular orientation of the perforating gun(s) with respect to the preferred vertical plane. Normally, the wellbore is then perforated after rotating the tubing; however, in the case of highly deviated and/or exceptionally deep wells, a second directional survey might be performed in order to confirm that the rotation applied to the tubing at the surface has been completely transferred to the downhole perforating gun(s). While use of tubing as the conveyance for the perforating gun(s), in combination with performing a direction survey, guarantees orientation accuracy, the procedure is relatively expensive, as it requires the use of both a workover rig for conveying the tubing, and, a wireline or slickline unit for running the direction survey.
Alternatively, the perforating gun(s) can be conveyed into the well using wireline as a conveyance, thus eliminating the need for a workover rig. One method of perforating using wireline is by employing the modular perforating method and apparatus disclosed in U.S. Pat. No. 5,366,014, titled “Method And Apparatus For Perforating A Well Using A Modular Perforating Gun System,” by George, incorporated in its entirety here within by reference.
FIGS. 1A and 1B
depict perforating a wellbore using a modular gun assembly. Initially, gun hanger
110
is inserted into casing
100
and positioned below formation
120
using collar locator
140
, which is attached through a cable head to a cable, either wireline or slickline. Gun hanger
110
is then set using a running tool
150
(shown in a cutaway view in order to view stinger
130
B). Running tool
150
and collar locator
140
are then retrieved from the wellbore, leaving stinger
130
A in an upturned position on top of gun hanger
110
.
With gun hanger
110
in position, modular perforating gun
160
, which includes upper gun head
180
and alignment skirt
170
, is run inside casing
100
using collar locator
140
and running tool
150
, similar to running gun hanger
110
into the wellbore. Alignment skirt
170
is coupled to upturned stinger
130
A, which causes perforating charges
162
to be positioned at depths adjacent to formation
120
(
FIG. 1A
depicts perforating gun
160
just prior to coupling of skirt
170
and stinger
130
A). Also included are centralizers
190
for centering alignment skirt
170
in casing
100
, for ensuring that alignment skirt will mate properly with stinger
130
A.
FIG. 1B
depicts a top view of casing
100
, which also shows the orientation of perforating gun
160
relative to preferred vertical plane
195
. Note that perforating gun
160
is loaded with perforating charges
162
, positioned at four shots per foot and oriented at a 90° phase from each other. In the above described shot configuration, no perforating charge is oriented in parallel with preferred vertical plane
195
. Instead, each of perforating charges
162
is oriented 45° away from the preferred vertical plane. Therefore, it would be expected that the wellbore would produce hydrocarbons at a lower rate than if perforating charges
162
were oriented in parallel with preferred vertical plane
195
. Note that, in the depicted example, only half of the perforating charges can ever be aligned with (or in phase with) preferred vertical plane
195
. The remaining charges will be oriented 90° away from preferred vertical plane
195
. Therefore, it is expected that the perforations created from those perforating charges will produce hydrocarbons at the lowest possible rate of any orientation.
In an effort to alleviate the above described shortcomings,
FIGS. 1C and 1D
depict perforating formation
120
, using an ultra high shot density perforating gun.
FIGS. 1C and 1D
show the same basic configuration as depicted in
FIGS. 1A and 1B
, with the exception of perforating gun
165
. Rather than being loaded with four perforating charges per foot at 90° phase displacement, perforating gun
165
is loaded with eight shots per foot at 45° phasing. Note that perforating gun
165
carries twice the number of perforating charges
167
as in the prior example. While loading a perforating gun with high shot density at a relatively low phase displacement increases the chances that formation
120
will be perforated parallel to preferred vertical plane
195
, there is no guarantee of success. Furthermore, the number of perforating charges expended in the effort is double, and the expense increases. Finally, because of size constraints o
Carstens David W.
Halliburton Energy Service,s Inc.
Herman Paul H.
Neuder William
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