Tubing elongation correction system & methods

Details Tubing elongation correction system & methods Tubing elongation correction system & methods

2002-02-08

2002-09-17

Schoeppel, Roger (Department: 3672)

Wells

Processes

With indicating, testing, measuring or locating

Reexamination Certificate

active

06450259

ABSTRACT:

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for determining the drilled distance between the surface and a point in a well bore. More particularly, the present invention relates to a system using a processor that calculates true measured depth based on data received from surface sensors, downhole sensors, and in another aspect, the present invention relates to a method for using a tubular umbilical to determine the drilled distance between the surface and a point in a well bore. More particularly, the present invention provides a method for correcting a surface-measured length of a tubular umbilical to determine the sub-surface length of the tubular umbilical by using an environmental profile to calculate length corrections. Still more particularly, the present invention relates to methods using temperature differentials, pressure differentials and axial loadings to correct a surface-measured length of a composite coiled tubing umbilical to determine the corresponding sub-surface length of the umbilical.
2. Background of the Invention
Successful hydrocarbon recovery operations are often founded on the ability to accurately log the trajectory of a drilled well bore extending hundreds or even thousands of feet below the surface of the earth. Accurate depth measurements can play an important, if not pivotal, role in such hydrocarbon recovery operations. Referring now to
FIG. 1
, “measured depth” (MD) is defined as a drilled distance between a surface point P
o
and consecutive points P
1
, P
2
. . . P
n
. In contrast, true vertical depth (TVD) is the distance between a point P and the surface point P
O
as measured on a vertical plane. Both MD and TVD are important for proper log data correlation. Because MD provides a basis for reference points along a drilled well bore, formation properties are often linked to accurate MD logs. With measurement-while-drilling (MWD) instrumentation, formation data such as gamma emissions and resistivity may be surveyed while a well bore is drilled. By logging the MD in conjunction with MWD surveys, formation data can be given a physical location with respect to the well bore trajectory. Once a well bore has been completed, a log for the well bore would show the formation properties at each MD. Such formation data can be used to determine which layers of formation are likely to hold hydrocarbon deposits. For example, it may be that the well log indicates that a gas layer exists at point P
i−1
, an oil layer exists at point P
i
(a “pay zone”), and a water layer exists at point P
i+1
. Because oil is far more profitable to recover than gas, well owners often wish to drain the oil layer without disturbing the gas deposits above the oil. This is even more the case with water layers because recovery of water is rarely, if ever, profitable. Moreover, it is usually very undesirable to inadvertently drain a gas or water layer because these fluids tend to flood a well to such a degree that a well remains nonfunctional until all the water or gas has been evacuated from the well. Further compounding the inherent difficulties in this situation is that, in many instances, a pay zone may be less than fifty feet in a well bore that may be thousands of feet in length. Therefore, it is important that well owners obtain well logs having accurate measured depths for subterranean formations in order to drain a pay zone without disturbing adjacent layers.
Further, regulatory authorities often require that owners of wells keep detailed formation survey information. Inaccurate data could lead to unintended violations of regulatory rules and subject the well owner to fines or other penalties. Therefore, accurate MD logs provide the well owner with the information needed to comply with the rules governing drilling activities.
Obtaining accurate MD logs is usually a fairly straightforward process for wells using drill string made up of conventional steel pipe or steel coiled tubing. For conventional steel pipe, the individual joints making up the pipe string are of a known length. Thus, an operator needs only keep count of the number of joints making up the pipe string. For example, referring to
FIG. 1
, if one hundred joints, each thirty feet in length, span between point P
o
and point P
i
, then the MD at point P
i
is 3000 feet. Similarly, when steel coiled tubing
20
is used, the length of steel coiled tubing
20
payed out from a reel
22
on the surface represents the MD. Often, the length of steel coiled tubing is measured as a function of the number of revolutions made by a friction wheel (not shown); coiled tubing length may be also measured by other commercially available line payout devices. For example, referring to
FIG. 1
, a dial (not shown) on reel
22
may indicate that 3000 feet of steel coiled tubing
20
was payed out between points P
o
and P
i
. Thus, the dial indicates a MD of 3000 feet at point P
i
. In either of the above instances, as long as the surface measurements are taken properly, the MD should also be accurate. It should be understood that the examples discussed are merely illustrative and to not represent expected depth values or measurement accuracy.
While these prior art MD survey techniques may be reliable for tubing formed of metals such as steel, however, such techniques do not give accurate logs for tubulars made of materials such as composites. Composite materials for coiled tubing are discussed in pending application Ser. No. 09/081,961, filed May 20, 1998 and entitled “Well System,” which is hereby incorporated by reference. Tubulars made of non-metals, such as composites, are susceptible to significant length changes due to factors such as temperature, pressure and axial loadings. Unfortunately, elevated temperatures, high operating pressures and complex compression and tension loadings are almost always present in a well bore environment. Thus, a length of composite coiled tubing on the surface may expand or contract as it enters a well bore. For example, a surface-measured length at reel
22
may indicate that 3000 feet of composite coiled tubing was payed out at point P
i
. However, the composite coiled tubing umbilical may have expanded to 3050 feet due to well bore conditions. Accordingly, the actual drilled depth at point P
i
would be 3050 feet, not 3000 feet. An uncorrected MD log can present serious problems in later operations when equipment such as perforation charges are tripped downhole to initiate the drainage of a pay zone at P
i
. Since this equipment is run in on a wireline or other device that is not subject to the same type or degree of expansion, the charge would be set at 3000 feet instead of 3050 feet, and possibly within the gas layer at P
i−1
. Indeed, even during successive composite coiled tubing trips for the same operation, downhole conditions can vary to a point where it may be difficult to correlate logs of these successive trips. Despite the critical need for accurate MD logs, the prior art does not disclose systems or methods that correct surface measurements of tubulars made of materials that deform when exposed to environmental factors.
BRIEF SUMMARY OF SOME OF THE PREFERRED EMBODIMENTS
The present invention features a system and method for determining a sub-surface length of tubulars made of materials that deform when exposed to environmental factors. The sub-surface length of the tubing generally represents the measured depth. For a well having a composite coiled tubing umbilical extending from the surface to a bottom hole assembly in a well bore, an embodiment of a preferred system includes a surface processor, surface sensors, downhole sensors and a telemetry system. The surface processor includes software that determines an environ-mental profile for the tubing using the environmental data retrieved by the downhole and surface sensors. By applying the environmental profile to the surface-measured length of the tubing umbilical, the compu

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