Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Earth science
Reexamination Certificate
2002-02-05
2004-12-28
McElheny, Jr., Donald E. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Earth science
Reexamination Certificate
active
06836731
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and system of determining overall well performance by the calculation of a well optimization index derived from a relation between well operation execution performance and the productivity of the well.
2. Description of the Related Art
In conventional systems, there is no single parameter in common use that allows operations groups to systematically assess the degree of success to which a well has been drilled or intervened.
Most parameters used today relate only to the particular area they are in, or are related to an Authorization for Expense (AFE) or plan generated by the executors themselves. Typically in oil companies today, a successful well is when the AFE targets for cost and time are achieved underbudget, or when these time or cost targets are improvements in the area of activity. Similarly for production targets, when historical rates are exceeded the well is considered a success. Clearly without comparisons to absolute or potential values, the true success or optimization of a well can not be concluded, and neither can any systematic cross-area comparisons be made.
Well optimization has two fundamental elements, well cost (or time), and well productivity. Typically parameters that express the performance in these two areas are kept separate, and as a consequence, it is not uncommon that very successful drilling performance is not mirrored in well productivity, or vice versa. At a minimum, it is commonly seen that the timing and degree of effort applied to each area is poorly synchronized.
Further, since in most projects, fundamental inputs to determine well optimization are not immediately available, and would require a significant effort to generate, achieving an understanding of optimum well times and production potential such that well optimization can be easily determined with a particular degree of accuracy, is necessary.
SUMMARY OF THE INVENTION
Methods and systems consistent with the present invention include the calculation of a common indicator for tracking trends and monitoring overall well performance—known as a well optimization index (WOI).
The WOI is calculated as a weighted average of two numbers reflecting operation execution performance (i.e., the Well Construction Operation Time Ratio (WCT
R
)) and production result performance (i.e., the Productivity Index Ratio (PI
R
)). The WOI is general for all kinds of well operations (i.e., oil or gas wells), such as drilling new wells or re-entering old wells, completions, workovers or rig-less work (i.e., stimulation, coiled tubing (CT), etc.).
The two indices WCT
R
and PI
R
each represent the performance of the well operation performed as compared to an optimum value. The WCT
R
can be calculated immediately after the well operation is completed, but the productivity index ratio PI
R
can only be calculated after the well production initiates and stabilizes. Because of this reason, the WOI index might not be available until a certain amount of data on the well operation is received.
Since production is typically of more ultimate value than the amount of cost that can be saved by reducing drilling or intervention times, the PI
R
term is weighted. Currently the proposed weighting is based upon “average” global production values versus “average” global well costs. The weighting is expressed as a constant, which represents recovery of cost.
In one embodiment, consistent with the present invention, the method of determining the WOI is carried out in a spreadsheet program used in a data-processing system, the program performing the method including the steps of generating a well construction time ratio WCT
R
for the well; generating a well productivity index ratio PI
R
for the well; and automatically generating a well optimization index WOI for the well based on a relation between the well construction time ratio WCT
R
and the well productivity index ratio PI
R
.
Specifically, in one embodiment consistent with the present invention, the WOI generating step includes automatically comparing a weighted average of an operation execution performance as defined by the well construction time ratio WCT
R
, to the production result performance as defined by the well productivity index ratio PI
R
, according to the following expression:
WOI
=
PI
R
N
+
WCT
R
N
+
1
;
wherein N is a weighting constant which represents a recovery of cost of a well operation, that is estimated based on historical data. In another embodiment consistent with the present invention, the WOI comparing step includes the step of inputting the weighting constant N from either an external source or a memory storage device.
In another embodiment consistent with the present invention, the WOI generation step includes the step of receiving a name of the well from an external source prior to the well construction time ratio WCT
R
generating step. The well construction time ratio WCT
R
generating step includes the step of automatically comparing a well construction theoretical limit WCT
L
, defined as a theoretical minimum rig time to execute a well operation, in days, to an actual well construction time WCT
L
, in days, in accordance with the following expression:
W
C
T
R
=
W
C
T
L
W
C
T
A
.
In one embodiment consistent with the present invention, the well construction time ratio WCT
R
varies from 1.0 in a best case where intervention time equals said predetermined technical limit WCT
L
, to zero in a worst case, where intervention would not be completed.
In a further embodiment consistent with the present invention, the well construction theoretical limit WCT
L
is a predetermined technical limit for each well type, and the well construction theoretical limit WCT
L
is either retrieved from the memory storage device or received from an external source.
In another embodiment consistent with the present invention, the well construction theoretical limit WCT
L
is an addition of actual best time of historical data for each phase for each well type, minus fifteen percent, and the well construction theoretical limit WCT
L
is either retrieved from a memory storage device or received from an external source.
In a further embodiment consistent with the present invention, the WCT
R
comparing step includes the step of receiving the actual well construction time WCT
A
from either the external source or the memory storage device.
In another embodiment consistent with the present invention, when a different rig is used to complete the well, the well construction theoretical limit WCT
L
and the actual well construction time WCT
A
are each calculated by adding drilling rig days plus completion rig days for the well, and the calculated well construction theoretical limit WCT
L
and the calculated actual well construction time WCT
A
are received from either the external source or the memory storage device.
In another embodiment consistent with the present invention, when the technical limit WCT
L
is not available, then the well construction time ratio WCT
R
is replaced by an operation cost ratio OC
R
, as defined by the following expression:
O
C
R
=
O
C
A
F
E
O
C
A
wherein:
OC
AFE
=Operational Cost as given by an Authorization For Expense
OC
A
=Actual Operation Cost; and
wherein when the OC
AFE
and the OC
A
are either retrieved from the memory storage or received from an external source, the OC
R
is automatically generated.
In another embodiment consistent with the present invention, the well productivity index ratio PI
R
generating step includes the step of automatically comparing an optimum productivity index PI
O
, in BFPD/psi (or BFPD/psi/foot of perforated interval), to an actual productivity index PI
A
, in BFPD/psi, in accordance with the following expression:
PI
R
=PI
A
/PI
O
.
In another embodiment consistent with the present inventi
Cancado Lino Lopes
Prato Jesus
Sandoval Luis
Whalley Robert
Echols Brigitte L.
McElheny Jr. Donald E.
Ryberg John J.
Schlumberger Technology Corporation
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