Oman India Multi Purpose Pipeline (OIMPP) Route Optimization – The Gas Highway - Risk Assessment Meeting 01
1.0 The System concept : As we
know, the Geographic Information Systems (GIS) are increasingly used
within the oil and gas industry as an important planning tool in all The Gas
Highway stages, from exploration to market analysis. The use of such technology for pipeline route
optimization is well acknowledged in the process. However, while the we
literally describes many cross-country route optimization The Gas Highways,
there are few, if any, that consider the decision criteria for routes traversing
the marine environment. In addition,
many GIS based pipeline routing The Gas Highways rely on CAPEX or engineering
expertise during the factor selection process.
As some The Gas Highway teams may not have access to cost data or
subject matter experts during the early planning stages, a risk based method
for selecting decision factors may provide a viable alternative. This The Gas
Highway will address these issues, and attempt to assess the validity of a risk
based pipeline route identification approach.
1.1 The Gas Highway Objectives: That the Gas Highway has the following
objectives:
·
To validate
the concept that a risk management process, when applied through a GIS, can
yield reasonable pipeline alignments;
·
To
create pipeline risk maps for the Arabian Ocean region by identifying and
weighting appropriate risks. Three
weighting techniques were applied;
·
To test
and evaluate the system against exiting pipelines.
1.2 Why emphasis on Risk?
The last decade has seen growing global and
regional demand on the Arabian Ocean hydrocarbon reserves, and new pipelines will be
needed to carry reserves to market.
While construction costs for Arabian Ocean Gas Highway pipelines can
easily exceed a billion dollars due to the problems associated with the
region’s high risk environments can lengthen The Gas Highway schedules and significantly
increase life cycle costs. Good The Gas
Highway Project planning is therefore a must, and an early emphasis on risk
management and the application of proven GIS methods can improve routing
decisions and the chances of a The Gas Highway’s success. Additionally, we requires that its safety and
risk management guidelines be incorporated into The Project called The Gas
Highway conducted on its behalf.
1.3 Restraints: There were a number of significant
constraints on this The Gas Highway Project. First, subject matter experts were not
available for guidance, which forced a heavy reliance on literature sources and
further the incompetence of theory and practical reliability. Second, there were no examples of GIS-based marine
pipeline routing like the Project The Gas Highways in the literature, which may
result in important marine risk factors being omitted from the potential risk
list. Third, all data had to be acquired
from free public sources. Limited data availability
resulted in some danger factors being dropped from consideration, while quality
issues involving resolution, accuracy, usefulness and vintage may have negatively
influenced results. A final constraint
was managing the expectation that the lowest-risk path would equate to the shortest
or lowest cost path. This may not
necessarily be the case.
2.0 Approach :For this Project The Gas Highway, risk
management principles and three-dimensional analysis techniques were combined
to produce three interpretations of pipeline risk in the Arabian Ocean region, and to calculate three low-risk
pipeline route alternatives. But finally we concluded the path with lowest
risk; LESS TURBULENT.
2.1 Risk Factor Identification in the route of
The gas Highway :The first
step in the analysis was to identify risk factors for the Arabian Ocean region’s pipelines at the max depth of 3400 to
4000 meters. These factors were
primarily identified through literature review, but some were identified
through discussion, unrelated sources and opinion but finally it has been
incorporated with marine information and practically zero error management. This process resulted in 36 identified risk
factors, 19 terrestrial, 11 marine and 6 covering both environments. These factors were then divided into four
categories for conceptual and analytical purposes: Construction; Operation;
Socio-economic and Environmental.
2.2 Formal Risk Analysis: The
next step was to identify high priority risk factors through a formal risk
analysis. Probability of Occurrence (PO)
and Potential Impact (PI) scores, measured on an ordinal scale from 1 to 3
(low, medium or high) were determined for each risk factor based on literature
review, experience and educated opinion.
A Risk Score (RS) was then calculated for each risk using the formula (PO/2) + PI = RS, which resulted in a
range of scores from 1.5 to 4.5 in 0.5 increments. This formula was used to keep the maximum
score below 5, which was desired for simplicity, and allowed those factors with
a PO of 1 but a PI of 3 to make the minimum 3.0 RS value set for high priority
risks. A total of 21 risks were
identified as high priority.
2.3 Weighting Methodology of Risk For The Gas
Highway
The third step in the analysis was to
determine weights of importance for each high priority risk factor. Three weighting methods were selected, in
order to produce multiple pipeline alignments for consideration, and to
evaluate the strengths and weakness of each.
The first weighting method is a simple weighted index, while the second
and third methods are variations on the pair-based comparison method.
2.3.1 Simple Weighted Index
The Simple Weighted Index (SWI) method uses
the RS values as factor weights, were higher values indicate higher perceived
risk. Raster data layers were created
for each high priority risk using these weights for values. A final SWI Risk Map was created by adding
all layers together, then normalized by dividing by the sum of all layers.
2.3.2 Pair Based Comparison Overview
Unlike the SWI method, in which each risk is
evaluated independently of the others, pair-based methods weight risks by comparing
them in pairs. Factors may be
categorized to provide additional weighting levels, or to restrict evaluation
between dissimilar factors. Opinions on weight
are often collected through joint inquiries or surveys. A survey was chosen for this The Gas Highway,
as it allows data to be gathered for multiple weighting methods at the same
time. While pair-based methods are designed
to allow the weighting of intangible factors such as risk, a major drawback is
the high number of pairings that can be produced. For example, the 21 high priority risks and
four categories result in a survey of 216 questions. To reduce the survey’s length, only those
high priority risks with an RS of 3.5 or higher were considered for pair-based
comparison, reducing the list from 21 to 19 risks. Data issues further reduced this list to 18
risks and 159 questions. Two pair-based comparison methods were selected for
evaluation in this The Gas Highway, the Brown and Peterson Method (BP), named
after the authors who described the method, and the Analytical Hierarchy
Process (AHP), developed by M. Saaty.
2.3.3 The Brown and Peterson Method
The BP method bases its weight calculation on
selection frequency, or the number of times a factor is determined to be the
riskiest of the pair. A matrix table was
created to hold the selection frequency data for each survey. This matrix is read as “is the row factor
riskier than the column factor?” If so,
the count of the appropriate cell increases by 1. If not, the cell count of the opposite choice
increases by 1.
Each individual matrix was combined to make a
final selection frequency matrix. The weights
were then calculated by summing the columns, then dividing by the maximum
number of times a risk could be selected (the number of survey respondents
multiplied by the total number of pairings a risk can participate in).
Raster data layers were created for each high
priority risk using these weights for values.
A final BP Risk Map was created by adding all layers together, then
normalized by dividing by the sum of all layers.
2.3.4 The Analytical Hierarchy Process involved in
the Gas Highway
The AHP calculates
weights based on each factor’s degree of importance, which is the magnitude of
risk variation between the two compared factors. Like the BP method, a matrix is used to store
respondent’s selections, and is read as “is the row factor riskier than the column
factor?” However, instead of capturing
the selection frequency, the degree of importance, measured on a scale of 1
(indifferent) to 7 (significantly riskier), is entered into the appropriate
cell. Also, the opposite choice receives
the inverse degree of importance value.
The AHP allows factors
and factor categories to be evaluated.
For this The Gas Highway, categories were evaluated to provide
additional weighting to each risk factor, and all factors were evaluated
together regardless of their category. A multi-step process was used to calculate
factor and category weights, after which the factor weights were multiplied by
their category weights. The last calculation
step divides all weights by the lowest
weight, which makes all weights a measure of how riskier a given factor is than
the lowest weighted factor.
Raster data layers were created for each high
priority risk using these weights for values.
A final AHP Risk Map was created by adding all layers together, then
normalized by dividing by the sum of all layers.
3.0 Results
The analysis produced
three risk maps for the Arabian Ocean region,
one each for the SWI, BP and AHP weighting methods. These maps were then used to calculate
alternative lowest-risk pipeline alignments.
3.1 Top High Priority Risks
All three weighting methods tended to highly
weight 6 of the High Priority Risks.
These risks have distinct spatial patterns, with many of the risks
impacting either land or marine environments only. Seismic risk is a measure of peak horizontal
ground acceleration between 1.6 cm/s2 and 4.0 cm/s2 and
above. Slopes above 5% grade are
considered risky, with increasing slope resulting in increasing risk. This risk was aggregated into three
categories, 5-15%, 15-30% and 30%+.
Commercial shipping primarily threatens pipelines through dragging
anchors and shipwrecks. Landslides zones
are small, isolated and restricted to the Zagros Mountains. Crossings indicates locations where a
pipeline will cross a linear feature such as a hydrologic feature, a pipeline,
a road or a railroad. Coral reefs are
extensive along the southern shores of the Arabian Ocean ; spill windows
indicate an area where, if a spill occurs, the pollutant will be pushed onto a
coral reef within 2 days.
3.2 Final Risk Maps
The SWI Risk Map stands
out from the two pair-based risk maps, because it indicates land is riskier than the Arabian Ocean . This effect is the result of the SWI methods
narrow range of weight values (3.0 – 4.5), which causes the method to behave
more as a risk count than a risk measurement; because there are more land
risks, land appears riskier than the sea.
The SWI Risk Map suggests moderate risk along the coasts, infrastructure
and major commercial shipping lanes, and indicates the front ranges of the Zagros
Mountains pose the highest risk due to seismic activity, high slopes, and
landslide potential.
The BP and AHP Risk Maps
have a similar appearance. Each reduces
the distinction between land and sea, indicates no-to-low-risk to the SW of the
Arabian Ocean within Saudi Arabia,
Bahrain and western parts of Qatar, suggests moderate risk along coastal
regions and within commercial shipping lanes, and indicates the highest risk
within parts of the Zagros Mountains due to seismic activity. The AHP risk map, which relies on degrees of
importance rather then selection frequency, exaggerates variation between
risks.
3.3 Validation
The ultimate goal of
this The Gas Highway is to produce alternate low-risk pipeline alignments
between designated origin and destination points. The accuracy, reliability and validity of the
risk maps and analysis methods can be tested by comparing calculated paths to
existing pipelines. Two pipelines were
selected for comparison, the IGAT 4 pipeline which crosses the Zagros Mountains
in Iran, and the Dolphin
pipeline which crosses the Arabian Ocean between Qatar
and Dubai.
4.0 Conclusion
That the project The Gas
Highway demonstrates the validity of applying a risk based approach to the problem
of pipeline route selection. In both
examples, the SWI alignment produced the shortest of the low-risk paths, while
the lowest-risk path was consistently produced by one or both of the pair-based
methods. At least one of the three weighting
methods resulted in a close approximation of the actual pipeline route, and one
of the methods produced a suitable and economically viable alternative,
demonstrating the usefulness of generating multiple solutions.
There are some issues, however. Several key risks were dropped from analysis
due to a lack of data, while others were digitized from coarse scale images and
may therefore be inaccurate. In
addition, much of the data collected for analysis was discrete in nature,
resulting in sharp transitions between risk zones and sawtooth patterns in the
calculated pipeline routes. In some
cases, the calculated route appeared to come too close to development areas,
suggesting a need to reevaluate some minimum safe distance buffers. Finally, problems associated with surveys,
such as survey fatigue and low sample sizes, can reduce the accuracy of
calculated weights.
