This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s).
B-9
SPE-164364-MS Unconventional Natural Gas Potential in Saudi Arabia Ali Sahin, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia
Copyright 2013, Society of Petroleum Engineers This paper was prepared for presentation at the SPE Middle East Oil and Gas Show and Exhibition held in Manama, Bahrain, 10–13 March 2013. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright.
Abstract Surge in the worldwide demand for natural gas, in recent years, has resulted in a considerable interest in the unconventional natural gas resources in many countries, including Saudi Arabia. Numerous studies indicate that the supply and demand balance can be achieved through the exploitation of unconventional resources which are located in the major hydrocarbon basins of the world. The scope of this paper is to review the main sources of unconventional natural gas with some emphasis on potential resources in the Arabian Peninsula, and to present initial results derived from a recent study of Paleozoic formations in the Rub’ Al-Khali Basin. Besides contributing to the general knowledge on unconventional natural gas resources, the information provided in this paper is expected to guide current exploration activities on the unconventional natural gas in Paleozoic formations in the Rub’ AlKhali Basin. Based on the lognormal model, it has been demonstrated that the volume of unconventional gas resources in a particular basin is several times that of the proved reserves in that basin. Considering this model, it is possible to deduce that vast amounts of unconventional resources exist in the Arabian Peninsula. Potential targets have been identified to be the Paleozoic formations, including Qasim, Sarah, Qalibah, Jauf, Unayzah, and Khuff. Average porosity and permeability measurements, based on the combined data from several vertical wells intersecting each formation in the Rub’ Al-Khali Basin, have been compared with the corresponding published data from the producing tight gas formations from North American basins. Porosity and permeability values, representing various formations in the Rub’ Al-Khali Basin, compare well with the corresponding parameters from North American basins. The same data, also, revealed the differences and similarities of patterns of distributions of petrophysical parameters in formations under consideration. Major technical contributions of this paper include: (1) appraisal of distribution of unconventional natural gas resources in the Arabian Peninsula, (2) characterization of natural gas potential of various formations, and (3) comparison of petrophysical parameters with the corresponding values from similar basins from North America. Introduction Rapidly increasing energy demand and the limited resources on the global scale have renewed interest on unconventional natural gas in many countries, including Saudi Arabia. Accordingly, the activities for exploration and development of unconventional natural gas resources world-wide have been intensified recently. With an approximately 4% (282.6 Tcf) of global natural gas reserves located mainly within the conventional reservoirs, Saudi Arabia appears to have a unique position in terms of natural gas reserves and potentials. Considering the favorable geologic setting of country, this figure is believed to be far below the expectations. Undoubtedly, this fact has added a further dimension for the special interest on unconventional natural gas, including tight sand gas and shale gas in the Kingdom. During the last three decades, major developments have taken place in the USA and Canada on the unconventional natural gas resources, especially on shale gas and tight sand gas (Holditch, 2003; Holditch, 2006; and King et al., 2010). Government incentives, improved technologies for drilling and completion as well as the relatively higher prices resulted in drastic increase in gas production from the unconventional resources. According to recently released figures, the USA produced 58% of its natural gas from the unconventional resources (mainly shale and tight sand) in 2011. Undoubtedly, this increasing trend is expected to continue in future. The USA case is considered as a success story by many and has further encouraged other
2
SPE 164364
countries, including Saudi Arabia, to explore, to assess the existing potentials, and to produce the unconventional natural gas from shale and tight sand resources. Obviously, we can benefit from the USA experience, especially from the developed technology considerably. However, we should keep in mind that each basin and each reservoir unit has its own unique characteristics requiring the detailed appraisals. Various published resource assessments indicate that the Middle-East has significant potentials for both shale gas and tight gas (Rogner, 1996; Kawata and Fujita, 2001; and Holditch, 2006). Major resources are believed to be locked mainly in siliciclastic and shale units of Paleozoic age. Therefore, tight sand, and shale gas exploration activities have been intensified in Saudi Arabia in recent years. Saudi Aramco has focused its attention to Paleozoic formations in the northwestern part of the Kingdom, whereas, International Joint Venture companies are exploring in the Rub’ Al-Khali Basin. The Paleozoic rock units crop out along a curved belt bordering the Arabian Shield located in the western part of the country, and dip gently to northeast, east and south-east. The outcrop belt is somewhat broader both in the north and in the south-east part of the country. The Palaeozoic units cover the entire subsurface in northern, eastern, and south-eastern Saudi Arabia and the Arabian Gulf reaching a total thickness of over 2500 m. (Nurmi, 1991). The main targets for unconventional natural gas are the Lower Ordovician Sarah, Silurian Qalibah, Devonian Jauf and Permian Unayzah formations. International Joint Venture companies are exploring for non-associated gas within the Paleozoic section in the Rub’ Al-Khali Basin since 2004. More than 15,000 km of 2D seismic data, 8,000 km2 of 3D seismic data have been acquired and processed, and a total of 24 exploration wells have been drilled. The targeted sand units exhibit low porosity, and very low permeability, similar to average porosity and permeability values reported from tight sand units from different basins in North America (Masters, 1979; and Meckel, 2010). It has been observed that some intervals exhibit relatively higher porosity and permeability values. Such intervals may represent “sweet spots” commonly observed in tight gas formations elsewhere (Law, 2002). After giving a brief review of main unconventional natural gas resources, this paper discusses the lognormal nature of the distribution of natural resources, including oil and natural gas. The lognormal distribution is highly significant, since it provides the basis for understanding of vast potential for unconventional gas believed to exist in the Arabian Basin in association with the Paleozoic silisiclastic and shale units. The lognormal distribution is followed by an outline of the characteristics of the main Paleozoic units considered as the potential targets for exploration, as pointed out earlier. The final section covers the presentation and discussion based on a comparative study involving some porosity and permeability data derived from the recent exploration activities in the Rub’ Al-Khali Basin, and the corresponding published data from the producing tight gas formations from several USA basins. Main Sources of Unconventional Natural Gas There are vast amounts of unconventional natural gas associated with various rock formations in different geological environments. The most common natural gas resources include Tight Sand Gas, Shale Gas, Coalbed Methane, and Gas Hydrates. Brief reviews of all of these resources are given in the following paragraphs. However, it should be noted that among these resources only Tight Gas and Shale Gas are believed to exist in huge quantities in the Arabian Peninsula Tight Gas (TG)
Tight Gas is found trapped in unusually impermeable rock formations with permeability generally less than 0.1 mD (Holditch, 2006). It is, commonly, associated with geological formations in deep basins as opposed to conventional gas occurring in structural highs in the form of anticlinal traps. Therefore, Tight Gas is, sometimes, referred to as Deep Gas, or Basin-Centered Gas (Masters, 1979; and Law, 2002). Tight gas resources are widely distributed all over the world, especially in USA, and Canada. However, the major challenges are finding “sweet spots” which exhibit relatively higher porosity and permeability, and developing technology to extract the gas in a cost effective manner (Tverberg, 2008). Although the production technology has improved considerably in recent years, it is still difficult to produce gas from tight formations economically. Horizontal drilling followed by hydraulic fracturing, usually in multi-stages, is required to make natural gas to flow in economic quantities. Shale Gas (SG)
Shale gas is the natural gas associated with shale formations widely distributed in sedimentary basins. Shale is an organic rich sedimentary rock considered as a common source for both petroleum and gas. In addition, shale also contains natural gas, generally, associated within its fractures and pores. Another form of association is the adsorption of natural gas at the surface of this rock. Production of natural gas from shales is highly challenging task, requiring horizontal drilling and hydraulic fracturing as in the case of tight gas production. Shale is the most common sedimentary rock with widespread distribution globally. At least 22 major shale plays, spread over more than 20 states, have been reported in the USA (2010). Shale formations are, also, distributed extensively in other parts of the world, including China, Latin America, Russia and the Middle-East, particularly Saudi Arabia.
SPE 164364
3
Coalbed Methane (CBM)
Natural gas (mainly in the form of methane) is commonly associated with coal seams or with the surrounding rocks. This gas, frequently, cause explosions and fatal accidents during mining activity. Permeability of coal matrix is negligible; almost all permeability is due to fractures (0.1 to 50 mD in case of USA coal seams). Thus, natural gas is mainly found within fractures. It is, also, common to find natural gas adsorbed at the surface and released into atmosphere during mining activity, and hence, causing explosions. Coal has widespread distribution in sedimentary basins in many parts of the world. The largest coal reserves are found in the USA, Russia, China, Australia and India. Gas Hydrates (GH)
Gas hydrates consist of molecules of methane locked within a lattice of ice. They were first discovered in permafrost regions and are extensively distributed in many parts of the world (Makagon, et al. 2007). Gas hydrates are believed to have formed under high pressure and low temperature conditions. Huge resources of gas hydrates exist in the world with estimates ranging between 7,000 Tcf and 73,000 Tcf. According to a USGS estimate, gas hydrates may contain more organic carbon than the world’s coal, oil, conventional natural gas combined together (www.naturalgas.org, 2010). Unfortunately, no technology has been developed yet to extract natural gas from gas hydrates. Distribution of Unconventional Natural Gas Resources It has been, commonly, observed that natural resources (including mineral deposits, petroleum, and natural gas) follow positively skewed lognormal distributions. Such type of distributions is particularly common when mean values are low, variances large, and values cannot be negative (Eckhard, et al., 2001). Considering the lognormal pattern of distribution, it can be simply deduced that higher grade resources are in short supply, whereas low grade resources are in abundance. In cases of natural gas and petroleum, it may, simply, be enough to study the distribution pattern of permeability values to understand this phenomenon. Positively skewed permeability distributions indicate that reservoirs with higher permeability values are only few, but lower permeability reservoirs make up significantly larger proportion of reserves and/or resources. As illustrated in Figure 1, great majority of discovered fields (mostly conventional reservoirs) represent the higher tail of the distribution, and a significant proportion of lower permeability reservoirs are awaiting discovery.
Resources
The positively skewed nature of permeability is valid at every scale from a single reservoir to a basin. Sahin and Saner (2001) reported positively skewed permeability distributions for three zones within the Arab-D reservoir in Abqaiq field. Numerous authors have shown that the same model can be valid for permeability in other reservoirs (Sahin and Hassan, 1998; Kelkar and Perez, 2002; and Abdulkadir, 2010). Obviously, it is possible to derive the permeability distribution for every basin and to determine approximately the amount of unconventional natural gas resources, yet to be discovered. The cut-off permeability between conventional and unconventional gas resources is, arbitrarily, taken to be 0.1 mD (Holditch, 2006). Considering this cut-off value in Figure 1, we can see that the area representing the conventional resources is only a small fraction of the area representing the unconventional resources.
Unconventional
Conventional 0.001
0.1
1.0
1.000
Permeability (mD)
Figure 1: Lognormal distribution of natural gas resources
The permeability-resources relationship can, also, be illustrated using a triangular diagram as commonly adopted in the literature. This diagram (illustrated in Figure 2) is a simplified version of the positively skewed distribution. The lower permeability resources represent the base of the triangle, whereas higher permeability reservoirs occupy its upper corner. Main resources of unconventional natural gas, outlined in the previous section, will plot in the red area in this figure with Gas Hydrates being closest to the base. Obviously, we have a dynamic system highly dependent on technology and prices. The relationship with prices and technological developments are also indicated in Figure 2. Higher permeability reservoirs are relatively easy to develop,
4
SPE 164364
whereas lower permeability ones are more challenging in terms of technology. Therefore, improvements in technology will make it easier to produce more from lower permeability reservoirs, and gradually as the technology advances lower permeability resources will be upgraded into reserves. The prices have somewhat similar effect on resources. As the prices increase, there is a tendency to move towards lower permeability area at the bottom of the triangle. Based on these facts, we can state that both increase in prices and technological developments will lead to significant reserve increases. Therefore, they should always be taken into consideration in any resource/reserve assessment task.
1,000 mD High Small volumes; easy to develop
Higher prices
Improved technology
1.0 mD Medium
0.1 mD Low
0.001 mD
Large volumes; difficult to develop
Figure 2: Resource triangle for natural gas
Potential for Unconventional Natural Gas in Saudi Arabia The world-wide distribution of unconventional natural gas resources is listed in Table 1 (Kawata and Fujita, 2001). These data were based on the data originally published by Rogner (1996). According to these data, Middle-East and North Africa has the third position in Shale Gas after North America and Asia (including China) regions. With regards to Tight Gas, Middle-East and North Africa region has also a significant potential ranking fourth in this list.
Table 1. Distribution of unconventional natural gas resources (after Kawata and Fujita, 2001) REGION
TYPES OF GAS (Tcf) SG
TG
3,017
3,840
1,371
8,228
39
2,116
1,293
3,448
W. Europe
157
509
353
1,019
Central and E. Europe
118
39
78
235
North America Latin America
Former Soviet Union M. East & N. Africa Sub‐Saharan Africa Asia (including China) Pacific (OECD) Other Asia Pacific
South Asia World
CBM
TOTAL
3,957
627
901
5,485
0
2,547
823
3,370
39
274
784
1,097
1,215
3,526
353
5,094
470
2,312
705
3,487
0
313
549
862
39
0
196
235
9,051
16,103
7,406
32,560
Natural gas resources in tight formations have been estimated to be approximately 54 times of the proved reserves in the USA (Holditch, 2006). Since the USA basins are well-studied with plenty of data, we can consider this figure to be reasonably reliable estimate. By analogy, we can assume that similar relationship most likely exist in other hydrocarbon basins of the world, including the Middle-East. Rogner (1996) estimated about 3370 Tcf of natural gas resources in the entire Middle-East and North Africa as shown in Table 1. Out of this total estimate, about 2547 Tcf is believed to be present as the shale gas and the remaining 823 Tcf as tight sand gas. Qusaiba Shale is, certainly, considered to be the major resource for the shale gas in the Middle-East, including Saudi Arabia. It should, however, be noted that even the tight sand gas estimate, given in Table 1, is adequate to increase Kingdom’s share of global gas production to over 16% from the current level of 4%.
SPE 164364
5
Potential Exploration Targets in Saudi Arabia As pointed out earlier, the main exploration targets are considered to be the reservoir rocks within the Paleozoic succession ranging from Early Ordovician to Late Permian, including Saq, Qasim, Sarah, Jauf, Unayzah and Khuff Formations. Among these, Saq, Qasim, Sarah, Jauf and Unayzah consist of siliciclastic and Khuff consists of carbonate rocks. Silurian Qusaiba Shale is, also, considered as a potential target on the basis of both its characteristics as a major source for the shale gas and its common association with the Rhuddanian Sandstone. Stratigraphically trapped within Qusaiba Shale, the latter has been interpreted as a basin-floor fan complex, and may provide places of accumulation for hydrocarbons, including natural gas (Hayton et al., 2010). Paleozoic units crop out along a curved belt surrounding the Cambrian and Pre-Cambrian rocks of the Arabian Shield as illustrated in Figure 3. The width of this belt is highly variable covering extensive areas in the north-western region, Al-QasimHail region and in the southern Arabia. The outcrop belt gets somewhat thinner in Central Arabia. Paleozoic units dip gently to north-east, east and south-east from the Arabian Shield, covering vast areas in the subsurface. In the Rub’ Al- Khali Basin, they are intersected at depths ranging from 14,000 ft. to 18,000 ft. and are considered to be tight formations on the basis of very low porosity (< 10%) and extremely low permeability values (< 0.1 mD). Both exploration and production from such formations are extremely difficult and pose highly challenging problems. A geological cross-section extending from Central Arabia to the Arabian Gulf Basin (eastern part of Qatar) is illustrated in Figure 4. The entire succession has been affected by uplifting and faulting associated with major structures such as Ghawar, Dukhan, and Southern Gulf Salt. Thickest part of the Paleozoic succession appears to be located to the east of the Ghawar structure.
North
30 A ra b ia n G ul f
26
S a u d i A r a b i a R e d
22
S e a
Arabian Shield Paleozoic
18
Mesozoic
Cenozoic Kilometers
0
250
500
14
Gu
Scale in Kilometers
36
40
44
48
lf
of
e Ad
n
Quaternary Sand Dunes Quaternary Volcanics
52
Figure 3: Simplified geological map of Arabian Peninsula
Figure 4: Geological cross-section from the Central Arabia to the Arabian Gulf Basin through Qatar (after Konert et al. 2001)
6
SPE 164364
The complete list of Paleozoic succession in Saudi Arabia is given in Table 2. The age, lithology and the thickness of each unit are given in this table. The total thickness of the entire Paleozoic succession is over 2530 m. with Saq and Qusaiba Shale both exceeding 600 m. (Nurmi, 1991) Some Paleozoic units, including Mid-Qusaiba Sandstone, Jauf, Unayzah, and Khuff are already proven reservoirs in other parts of Saudi Arabia (Hayton et al., 2010). Based on their overall characteristics, Sarah and Unayzah are considered the most prominent exploration targets among these units. Table 2. Potential exploration targets in Saudi Arabia PERIOD
ROCK UNIT
LITHOLOGY
THICKNESS (m)
Shallow marine and tidal channel fill carbonates
500
M. PERMIAN/ UNAYZAH L. CARBONIFEROUS
Braided fluvial, glacio‐fluvial, and eolian sandstones
180
DEVONIAN
JAUF
Shallow marine sandstones, limestones, and some shales
300
SILURIAN
QUSAIBA
Deep marine shales/hot shales and interbeded sandstones
600
L. ORDOVICIAN
SARAH
Braided fluvial, glacio‐fluvial, and glacially deposited sandstones
150
M. ORDOVICIAN
QASIM
nearshore marine sandstones, and shelf‐offshore marine shales
200
Thickly beded, conglomeratic sandstones, and partly large scale cros‐bedded sandstones
600
L. PERMIAN
KHUFF
E. ORDOVICIAN/ SAQ CAMBRIAN
Some exploration activities have been conducted on the selected Paleozoic units in the Rub’ Al-Khali Basin during the recent years. Average porosity and permeability measurements, as well as their ranges based on the combined data from nine vertical wells intersecting each formation in a particular area are presented in Table 3. As listed in this table, Unayzah-A has the highest average porosity and Qusaiba Shale has the lowest. There is a considerable range for porosity values in most rock units, except Saq, Qasim and Jauf formations. Lower ranges in these formations can partly be explained by the lower number of samples as shown in the table. Permeability ranges in most units are even greater with the highest value observed in Khuff Formation. Considerable range in parameters is partly due to highly variable nature of rock units, and partly due to the presence of sweet spots with relatively higher porosity and permeability values. Table 3: Porosity and Permeability Data for Paleozoic Units POROSITY (%)
PERMEABILITY (mD)
ROCK UNIT
CORE LENGTH (ft)
NO. OF PLUGS
0.4411
123.7
118
0.0008‐9.4181
0.5986
118.78
114
5.82
0.0015‐10.92
0.2605
60.82
67
4.91‐6.77
5.71
0.4306‐5.6962
2.5881
23
27
QUSAIBA
0.20‐2.79
0.54
0.0010‐0.2695
0.0183
28.5
29
SARAH
0.31‐12.88
3.76
0.0058‐8.8437
0.3155
142.72
137
QASIM
5.11‐5.46
5.29
0.0108‐0.0153
0.0131
1.7
2
SAQ
4.31‐5.98
4.78
0.0258‐0.2279
0.1351
5.75
6
Min‐Max
Average
Min‐Max
Average
KHUFF
0.28‐14.56
3.22
0.0003‐9.8303
UNAYZAH‐A
0.32‐17.61
6.52
UNAYZAH‐B
0.50‐11.90
JAUF
SPE 164364
7
Comparison of Petrophysical Parameters Porosity, permeability, and water saturation data representing nine producing Paleozoic tight gas formations from five USA basins are listed in Table 4. The ranges and average values of both porosity and permeability compare well with the corresponding combined data representing Paleozoic units from the Rub’ Al-Khali Basin presented in Table 3. The most striking characteristics of the data representing USA basins are very low permeability values with considerable ranges as observed in our data from the Rub’ Al-Khali Basin. Table 4: Petrophysical parameters of the producing USA Paleozoic Tight Sands (after Meckel, 2010) POROSITY (%) BASIN
ANADARKO
APPALACIAN FORT WORTH PERMIAN VAL VERDE
PERMEABILITY (mD)
SW (%)
FORMATION
Min‐Max
Average
Min‐Max
Cherokee
1.0‐18.0
9.0
0.1‐20.0
Average
Min‐Max
Cleveland
3.0‐14.0
8
0.001‐20.0
0.14
30‐40
Granite Wash
4.0‐12.0
8.5
0.0009‐1.0
0.012
22‐35
Clinton
2.0‐16.0
0.003‐6.0
20‐35
Berea
4.0‐17.0
0.002‐0.02
8.0‐50
Davis
2.0‐9.0
5.5
0.021‐0.031 0.01‐0.19
Abo
2.0‐15.0
14
Morrow
3.0‐17.0
8
Canyon
2.0‐15.0
7.5
Average
20‐35
0.08
35
15‐30 25‐60
35
8.0‐57
27
0.001‐0.052
20
To enable visual comparison of the data from the Rub’ Al-Khali and USA basins, they have been presented in the same table (Table 5). It should be noted that the USA data has been compiled from various agencies, including Bureau of Economic Geology, Department of Energy, and Gas Research Institute, and represents a total of 23 units from 13 basins (Meckel, 2010). It should be pointed out that considerable variation exists between petrophysical parameters of individual formations from both the Rub’ Al-Khali and USA basins, as demonstrated by the spread of values in the table. However, the data from the Rub’ Al-Khali Basin have revealed slightly lower porosity and relatively higher permeability than the corresponding parameters from the USA basins. As shown in Table 5, The Rub’ Al-Khali data occupies a distinct area at the top left corner of table. As it was expected, tight gas units, including Jauf, Unayzah, Khuff, and Sarah, exhibit relatively greater permeability than that of Qusaiba Shale. With regards to porosity, Jauf and Unayzah exhibit the highest porosity values ranging between 5 and 6%, and Qusaiba Shale has the lowest with 0.54%. Table 5: Comparison of petrophysical parameters: USA basins and the Rub’ Al-Khali POROSITY (%)
PERMEABILITY (mD) X.0 Units
.X Tenths
.0X Hundredths
.00X Thousandths
1 – 2 3 – 4 5 – 6 7 – 8 9 – 10 11 – 12 13 – 14 Code: Qusaiba Sarah Khuff Unayzah Jauf USA TG Sands
8
SPE 164364
Conclusions The major conclusions drawn from this study are summarized as follows: 1.
Unconventional natural gas is associated with diverse resources in diverse environments, including tight sands, shale gas, coalbed and gas hydrates. Among these resources, only tight sands and shales are present in vast amounts in Saudi Arabia.
2.
Based on the lognormal distribution of natural resources, it is possible to deduce the amount of unconventional natural gas resources in a particular basin. Because of the characteristics of lognormal distribution, the volume of unconventional natural gas resources in a particular basin is several times of available conventional reserves in that basin.
3.
Potential exploration targets for unconventional natural gas in Arabian Peninsula are the Paleozoic succession, including Qasim, Sarah, Qalibah, Jauf, Unayzah, and Khuff formations. Although the outcrops of these formations are relatively limited along a curved belt surrounding the Arabian Shield, they are extensively distributed in the subsurface.
4.
Comparison of the porosity and permeability data representing Paleozoic succession from the Rub’ Al-Khali Basin with the corresponding data from the producing tight gas formations from several USA basins indicates close similarities between these data.
5.
Unconventional problems require unconventional solutions. Therefore, it is essential to adopt unconventional approach to solution of unconventional natural gas exploration and production problems.
Acknowledgements This study was conducted at the Center for Petroleum and Minerals, Research Institute, King Fahd University of Petroleum and Minerals (Dhahran, Saudi Arabia). The author would like to acknowledge the support of authorities in this institution. The support of company which provided data for the study is, also, highly appreciated. References Abdulkadir, I. T., Sahin, A., and Abdullatif, O. M. (2010). Distribution of petrophysical parameters in the Cambro-Ordovician Dibsiyah Member of the Wajid Sandstone, SW Saudi Arabia. Journal of Petroleum Geology, 33(3), 269-280. Dong, Z., Holditch, S. A., McVay, D. A., and Ayers, W. B. (2011). Global unconventional gas resource assessment. Paper presented at the Society of Petroleum Engineers - Canadian Unconventional Resources Conference 2011, CURC 2011, 1, 810-825. Eckard, L., Werner, A. S., and Markus, A. (2001). Log-normal distributions across the sciences: keys and clues, BioScience 51(5), 341-352. Hayton, S., Heine, C. J., Gratto, B. (2010). Tight Gas Exploration in Saudi Arabia. Paper SPE 131065, presented at the SPE Deep Gas Conference and Exhibition, Manama, Bahrain, 24-26 January 2010. Hayton, S., Heine, C. J., Sherba, E. E., Gratto, B., Shenggen, Z., Shicheng, W. (2010). A new exploration play for Saudi Arabia, Paper SPE 131063, presented at the SPE Deep Gas Conference and Exhibition, Manama, Bahrain, 24-26 January 2010. Holditch, S. A. (2003). The increasing role of unconventional reservoirs in the future of the oil and gas business. JPT, Journal of Petroleum Technology, 55(11), 34-37+79. Holditch, S. A. (2006). Tight Gas Sands. JPT, Journal of Petroleum Technology, 58(6), 86-94. Kawata, Y. and Fujita, K. (2001). Some Predictions of Possible Unconventional Hydrocarbon Availability until 2100. Paper SPE 68755, presented at the SPE Asia Pacific Oil and Gas Conference, Jakarta, 17–19 April 2001. Kelkar, M. and Perez, G. (2002). Applied Geostatistics for Reservoir Characterization, Society of Petroleum Engineers, 264p. King, K. C., Greeser, B., Jaripatke, O., and Passman, A. (2010). A Completion Roadmap to Shale-Play Development: A Review of Successful Approaches towards Shale-Play Stimulation in the Last Two Decades, Paper SPE 130369, presented at the CPS/SPE International Oil and Gas Conference and Exhibition, Beijing, China, 8-10 June 2010. Konert, G., Afifi, A. M., Al-Hajri S., and Droste, H. J. (2001). Paleozoic Stratigraphy and Hydrocarbon Habitat of the Arabian Plate, GeoArabia, 6 (3), 407-442. Law, B. E. (2002). Basin-Centered Gas Systems, AAPG Bulletin, 86, 1891–1919. Makogon, Y. F., Holditch, S. A., and Makogon, T. Y. (2007). Natural gas-hydrates - A potential energy source for the 21st century. Journal of Petroleum Science and Engineering, 56(1-3), 14-31. Masters, J. A. (1979). Deep Basin Gas Trap, Western Canada. AAPG Bulletin, 63(2), 152-181.
SPE 164364
9
Meckel, L. (2010). Course Notes on Tight Gas Exploration, the EAGE Second Middle East Tight Gas Reservoirs Workshop, 12-15 December 2010. Nurmi, R. (1991). Old Sandstones New Horizons, Middle-Eat Well Evaluation Review, 11, 1991. Rogner, H. (1996). An assessment of world hydrocarbon resources. Annual Review of Energy and the Environment, 22(1), 217-262. Sahin, A. and Hassan, H. M. (1998). Enhancement of Permeability Variograms Using Outcrop Data, Arabian Journal of Science and Engineering, 23(1C), 137-144. Sahin, A., and Saner, S. (2001). Statistical distributions and correlations of petrophysical parameters in the Arab-D reservoir, Abqaiq oilfield, Eastern Saudi Arabia. Journal of Petroleum Geology, 24(1), 101-114. Spencer, C. W. (1989). Review of characteristics of low-permeability gas reservoirs in western United States, AAPG Bulletin, 73(5), 613629. Tverberg, G. (2008). US natural gas: the role of unconventional gas, original article: http://www.theoildrum.com/node/3981 the Oil Drum, May 18 2008. US Energy Information Administration (2011). World Shale Gas Resources, www.eia.gov/analysis/studies/worldshalegas/. US Energy Information Administration (2011). Review of Emerging Resources: US Shale Gas and Shale Oil plays, www.eia.gov/analysis/studies/usshalegas/. www.naturalgas.org/ (2010). Focus on Shale. www.naturalgas.org/, (2010). Unconventional Natural Resources Xiong, H., and Holditch, S. (2006). Will the Blossom of Unconventional Natural Gas Development in North America be repeated in China, Paper SPE 103775, presented at the SPE International Oil and Gas Conference and Exhibition, Beijing, China, 5-7 December 2006.
