Hydraulic Fracturing Technique To Improve Well Productivity and Oil Recovery in Deep Libyan Sandstone Reservoir
Hydraulic Fracturing Technique To Improve Well Productivity and Oil Recovery in Deep Libyan Sandstone Reservoir
Hydraulic Fracturing Technique To Improve Well Productivity and Oil Recovery in Deep Libyan Sandstone Reservoir
Saleh Arwini*
Department of Petroleum Engineering, University of Tripoli, Tripoli, Libya
* Corresponding Author: s.arwini@uot.edu.ly
Abstract
Hydraulic fracturing has become an important technique to improve well production and the recovery
of low-permeability reservoirs in the oil and gas field development. Worldwide there are vast reserves of
hydrocarbons trapped in tight sandstone formation. To produce this huge amount of reserve from low
permeability formation economically, hydraulic fracturing can be applied. This paper discusses the analysis
of pressure and production data from successful hydraulic fractured vertical well in low permeability Nubian
reservoir. Based on several screening criteria, the vertical oil well from Nubian sandstone reservoir was
selected for stimulation job by hydraulic fracturing. Several hydraulic fracture models have developed to
optimize hydraulic fracture in order to increase the productivity index of the subject wells. All Pressure
and production from the pre and post-hydraulic fracturing treatment data were collected and analyzed
to assess the job success in terms of effective fracture parameters, fracture conductivity and reservoir
parameters. Based upon the results of these results, the oil production rate of the subject wells is improved
dramatically by 10 times with a significant decrease in the formation damage near the wellbore. Therefore,
the success of the fracture treatment is largely due to efficient candidate selection, project management,
fully integrated project team and systematic application of existing hydraulic fracturing techniques.
Keywords: Hydraulic fracturing; low permeability reservoir; Nubian sandstone reservoir; well
productivity and oil recovery; formation damage.
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area of formation and bypasses any damage that seismic data. Currently, the estimated ST OOIP is
may exist in the near-wellbore area. Complexity over five billion barrels of OIP of 43◦ AP I gravity.
arises from two directions: geologic reality and the North Gialo is expected to produce 100, 000 bpd of
inherent multidisciplinary nature of the fracturing crude and 5.7 million cubic feet per day of gas [6, 7].
process [3, 4]. To assess the stimulation efficiency,
we need to estimate reservoir and hydraulic fracture
Figure 2.1: Eastern Sirte Basin Structural Features Map.
properties, such as effective permeability, fracture
half length and fracture conductivity. The knowl-
edge of these parameters are not only important for
predicting future production performance of frac-
tured wells, but also have significant impact on de-
termining development strategies in exploitation of
tight reservoirs, which has increased in recent years
[5]. This paper presents and discusses a successful
hydraulically fractured vertical tight oil well in deep
Libyan sandstone reservoir. All Pressure and pro-
duction from the pre and post-hydraulic fracturing
treatment data were collected and analyzed to assess
the job success. It is well-known that the purpose
of fracture treatment is to remove reservoir damage
near the wellbore, reduce total skin factor, increase Structurally, the field is bisected by numerous faults,
reservoir permeability near the wellbore and increase the western side of the field is dominated by NNW-
well production. SSE-trending faults, while the eastern side is domi-
nated by faults trending WNW-ESE. The NW part
of the field is further bisected by several major faults
with throw from 300’ to 1000’, separating the field
2. Field Description into major fault blocks. This major NNW trend-
ing fault (Figure 2.2 and 2.3) separates the X1 from
The North Gialo Field is situated in the eastern the Farigh field continues southeast just west of the
portion of the Sirte Basin at the intersection of the 4C-159 well and trends along the up dip limit of
Hameimat and Ajdabaiya troughs on the northern the UNS sub-crop. Moreover, the reservoir is con-
flank of the Gialo structural high as shown in Figure sidered a tight sandstone reservoir, which belong to
1. The prospective area of the Sirte Basin occupies the lower part of Lidam Nubian Sandstone forma-
about 230,000 km2 . A new structural-stratigraphic tion (Late Cretaceous age), and the reservoir found
play concept was developed by Waha in 1995 that at depth 12, 555 f t [6, 7].
led to the acquisition of a 3D seismic survey. Based
on the interpretation of the 3D seismic data, an Figure 2.2: Schematic North Gialo Structural/Stratigraphic
exploration well was proposed and drilled in early Model.
2002. North Gialo Field was discovered with the
drilling and testing of the 6J-1 well in early 2002.
During 2002-2004, the well intermittently produced
for a total of 129 days with cumulative produc-
tion of 338 M BO, representing an average rate of
2620 bbl/day. The discovery was based on inter-
pretation of the 3D seismic survey, data obtained
by the 1970’s four exploratory wells and the Farigh
Field to the Northwest. An additional 17 appraisal
wells were subsequently drilled to define the limits of
the field, fluid contacts and define the characteristics
of the reservoirs. Waha estimates, given the present
data, that the field covers more than 108 square kilo-
meters. The eastern and southern extensions of the
field are still to be defined by recently acquired 3D
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Figure 2.3: North Gailo, field structure map. Table 3.1: General information for selected candidate well.
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4. Results and Discussion Table 4.1: Pre and Post frac IPR’s Analysis.
28
Geophysics), it was essential that each team mem- [4] Mattax, C. C.; Dalton, R. L. Reservoir simu-
ber fully bought into the project and took owner- lation: Richardson, Society of Petroleum Engi-
ship of their individual responsibilities. Therefore, neers. Texas, 1990.
fully integrated project team was totally critical
to the overall success of the frac project. [5] Dmour, H. N.; Shokir, E. M. Pre-Post Frac Test
Data Analysis For Hydraulically Fractured Ver-
tical Tight Gas Well- Field Case Study. Oil and
Gas Business Journal, Russia, 2008, ISSN 1813-
Abbreviations 503X.
[6] Anon. Evaluation Report for Candidate Well
API American Petroleum Institute X1. Waha oil Company Tripoli, 2015.
AOFP Absolute Open Flow Potential
DST Drill Stem Test [7] Zanatı, M.; Sarı, R.; Canales, H. New Gi-
GOC Gas-Oil-Contact ant Hydrocarbon Dıscovery in Sirte Basin,
HSP High Strength Proppant Libya. EAGE-EarthDoc, 18th International
IPR Inflow Performance Relationship Petroleum and Natural Gas Congress and Ex-
LNSS lower Nubian Sandstones hibition of Turkey, May 2011.
Thousand Barrels of Oil (M = 1000
MBO
and MM = 1 million)
OIP Oil Initial in Place
OWC Oil-Water-Contact AppendixA.
PI Productivity Index
PTA Pressure Transient Analysis
Acknowledgment
References
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Table A.1: Data required for hydraulic fracturing design.
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Figure A.1: wellbore diagram.
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