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	School of Engineering COURSEWORK SUBMISSION SHEET
All sections except the “LATE DATE” section must be completed and the declaration signed, for the submission to be accepted. Any request for a coursework extension must be submitted on the appropriate form (please refer to http://www.rgu.ac.uk/academicaffairs/quality_assurance/page.cfm?pge=44250), prior to the due date.

Due Date	Date Submitted	For official use only
13 November 2011	12 November 2011	LATE DATE

MATRIC No. 1101006
SURNAME KAIRBEKOV
FIRST NAME(S) Daulet
COURSE & STAGE Eg MSc Oil & Gas Engineering MSc Drilling & Well Engineering	Full time
MODULE NUMBER & TITLE	ENM 200 SUBSURFACE
ASSIGNMENT TITLE	The fieldtrip report
LECTURER ISSUING COURSEWORK	Dr BRYAN CRONIN

I confirm: (a) That the work undertaken for this assignment is entirely my own and that I have not made use of any unauthorised assistance.

(b) That the sources of all reference material have been properly acknowledged.

[ NB: For information on Academic Misconduct, refer to http://www.rgu.ac.uk/academicaffairs/assessment/page.cfm?pge=7088]

Signed ………DAULET KAIRBEKOV………............ Date.......12/10/2011.............................

Marker’s Comments
Marker	Grade

Abstract.

The purpose of this report is to analyze the geological characteristics of Hopeman sandstone formation based on own observations. During this field trip evaluation of rock properties was carried out. Evaluations were based on determining and interpretation of grain properties, permeability, porosity and cementation features etc. On the basis of these estimates the sedimentary conditions were determined. Several localities on Hopeman sandstone formation such as Covebeach sandstone, Covesea cliff, Covebay sandstone, Daisyrock sandstone, Qlashach quarry and Burghead locality were visited. The main source of this report are own observation of student, pictures and recordings made during field trip, information which was given by lecturer.

Introduction.

It will be useful to make overview of the history of the Moray Firth before discussion. The British Isles were the part of vast continent called Pangea. A slow northwards drift of the Laurasian plate led to climate change from humid equatorial environment to arid conditions. At this Rotliegend period (Late Permian 260 mln years ago) the Moray Firth started to form along with rifting and subsidence of crust. As the climate was becoming increasingly arid sedimentation of sand dunes took place. Thereafter the area was flooded due to global rise of sea level called Zechstein transgression. It was assumed that the surface of the current Moray Firth was well below the open ocean level. Therefore the transgression continued until it matched that of the open ocean. The transgression led to sedimentation of shallow-marine carbonates. The following Triassic age brought back hot, continental conditions with strong winds which were the main force of transporting sediments. It represented onshore by Hopeman sandstone formation which is Aeolian origin (Glennie). The Jurassic-Cretaceuos period left a big mark on the entire surface of the North Sea and Moray Firth in particular in the form of faults and grabens.

Objectives.

The objectives are to make an observation and determination of main features such as porosity, permeability, fracturing and mineral compsition of exposed rock pattern by detecting following parameters: grain size, grain shape, grain sorting, rock color, structural type, compaction, cementation and depositional environment. Use observed information to characterize reservoir properties of given sedimentary rocks.

Data section.

Location #1: Covesea beach.

Rock type	Sandstone
Rock age	Late Permian (255 mln)
Sedimentary environment	Desert (Aeolian)
Sedimentary structure	Cross bedding (inclination - 10-15^0)
Grain size	Fine to medium
Grain shape	Rounded
Sorting	Well sorted
Color	Light brown to red
Compaction	Moderate
Cementation	Moderate (CaCO3, BaSO4)
Porosity	Good
Permeability	Good

According to shapes of cross beddings it can be assumed that these rocks were formed in desert conditions (Figure 1). The rounded shape, fine size and well sorting of sand particles is a result of strong winds which transported these particles far from source rock (Figure 2). Basically the SW winds made sand particles collide with each other and split to smaller parts. It also led to separation of sand particles by size, which means that they became more homogeneous. The cementing agents were formed due to natural seepage of fluids through the pores under lithification process. The pore spaces on sandstone are a result of weathering processes and moderate cementation (Figure 3). Therefore it can be assumed that this rock has good porosity and permeability. It should be mentioned that the color of the layers varies from light brown to red and grey in some places due to presence of small amount of ferric oxide.

Figure 1. Cross beddings on Covesea beach sandstone.

Figure 2. Grain shape, size and sorting characteristics.

Figure 3. Pore spaces on sandstone.

Location #2 Covesea cliff

Rock type	Sandstone
Rock age	Late Permian
Sedimentary environment	Desert (Aeolian)
Sedimentary structure	Cross bedding (inclination - 25-30^0)
Grain size	Fine
Grain shape	Rounded
Sorting	Well sorted
Color	Brown to red
Compaction	Moderate (cemented seams)
Cementation	Moderate (Carbonate cement, ferric oxide)
Porosity	Good
Permeability	Moderate

In accordance with observations the most of characteristics of this sandstone are identical to previous location, but there are some distinctions related to way of cementing. It should be noted that there are small quantity of ferric oxide (hematite). According to Maurice Tucker (sedimentary petrology, 1991, Blackwell science, 2^nd edition, p.61), only 0.1% of iron is sufficient to impart a bright red color to the sediments (Figure 4). It can also be observed that there are some cemented fractures (barriers) which were formed due to horizontal compression of layers and its further consolidation by barium sulfate (BaSO₄) (Figure 5). Difference in pressure of two separated sections could be significant. In case of fracturing during extraction of hydrocarbons it can seriously influence to production process. Consequently this sandstone is less attractive to be reservoir than previous one.

Figure 4. Hematite typically occurs as a very thin coating around grains.

Figure 5. Cemented fractures may form significant barriers to flow.

Location #3. Qlashach quarry.

This pattern of sandstone is the best evidence of the age of whole Hopeman sandstone formation. The footprints of ancient reptiles are clearly seen on sandstone blocks. It is assumed that the age of these footprints varies from late permian to early Triassic.

Figure 6. Fossil footprints of ancient reptiles.

Location #4. Cove bay.

Rock type	Sandstone
Rock age	Late Permian
Sedimentary environment	Desert (Aeolian)
Sedimentary structure	Cross bedding (inclination - 25-30^0)
Grain size	Fine
Grain shape	Rounded
Sorting	Well sorted
Color	Light brown
Compaction	Moderate (cemented seams)
Cementation	Poor (Silicate cement)
Porosity	Good
Permeability	Good

This pattern of sandstone demonstrates there was an old extension period in Jurassic before compression due to the tectonic plate movement. So it is a reactivated fault. It was observed that there are high angle fault (60⁰-65⁰) which consist of foot wall (on the left) and hanging wall (on the right) (Figure 7). The main feature of these walls is that they have different type of cementation. The hanging wall has poor cementation. It can be seen by the cave which was formed under the influence of the ocean (Figure 9). The foot wall is impermeable due to strong cementing. There was detected glass particles reflecting light and it was suggest that sand should have been under temperature treatment. Therefore it is acting as a trap which prevents the migration of fluids (Figure 9). Based on this facts it should be noted that this sandstone is the most attractive to be source rock.

Figure 7. The foot wall (on the left) and hanging wall (on the right).

Figure 8. Cave eroded by the sea water.

Figure 9. Hard cemented foot wall.

Location #5. Daisy rock

Rock type	Sandstone
Rock age	Late Permian
Sedimentary environment	Desert (Aeolian)
Sedimentary structure	Cross bedding (inclination - 10-15^0)
Grain size	Fine to medium
Grain shape	Rounded
Sorting	Well sorted
Color	Brown to grey
Compaction	Moderate (cemented seams)
Cementation	Good (Silicate cement)
Porosity	Low
Permeability	Low

This sandstone formation differs from others. The main features of this sandstone are hard cementing, low porosity and low permeability. Figure 10 can serve as an example of impermeability. As it seen water on rock surface doesn’t seep through this rock. Some quartz particles can be detected and this could be an explanation of hard cementation. The sandstone has high amount of vertical fractures due to exposure to weathering (Figure 11). According to observations this sandstone has bad reservoir properties.

Figure 10. Impermeability of Daisy Rock sandstone.

Figure 11. Consequences of erosion by sea water

Figure 12. Cross beddings on Daisy rock sandstone.

Location #6. Burghead sandstone.

Rock type	Sandstone
Rock age	Triassic
Sedimentary environment	Ancient river environment (Alluvial)
Sedimentary structure	Cross bedding (inclination - 10-15^0)
Grain size	Medium
Grain shape	Sub rounded
Sorting	Well sorted
Color	Brown to grey
Compaction	Good
Cementation	Good (Carbonate cement)
Porosity	Good
Permeability	Good

The Burghead sandstone consists of fluvial-channel deposits which mean that it was formed in ancient braded river conditions. It can also be assumed that there was a period when this area was exposed to flooding which are determined by sequence of various layers of sands, pebbles and silts (Figure 13). It requires high energy to transport big particles such as gravels far from source rock. The difference in layers (composition) explained by changing in force and direction of the channels (Figure 14).

Figure 13. Difference in composition: silt and gravels.

Figure 14. Cross bedding on Burghead sandstone.

Conclusion.

This report has been written based on own observations of student, explanations of lecturer and theoretical knowledge gained during classes. Surveillances consist of determining of porosity, permeability by investigation of grain properties, analyzing and interpretation of gained information. Proceedings from these data following conclusions were drawn:

Ø The Hopeman sandstone formation was formed in desert conditions during Permian age.

Ø Basically the south-west winds transported the sand particles far from source rock.

Ø Coastal part of Hopeman sandstone formation was uplifted due to movement of tectonic plates.

Ø The Hopeman sandstone formation has good reservoir properties especially Covesea beach and Covebay sandstone formations.

Ø The properties of rocks in different localities are not similar. It is explained by the fact that they were exposed to different kinds of influence such as weathering, lithification process, tectonic plate movements etc.

Ø The importance of this trip is very high. It helps future specialists to acquire skills which they can use in decision-making.

References:

Cronin, B., 2009, The Moray Firth: Overview of Petroleum Systems from Field Geology.Aberdeen. Unpublished.

Tucker, M., 2^nd ed., 1991, Sedimentary petrology, Blackwell science, p.61

Glennie, K. W., 1998, Petroleum geology of the North Sea: basic concepts and recent advances. (electronic resource). Available from: http://resourcelists.rgu.ac.uk/lists/BDD06F7F-C894-88A5-69FE-C4F6C88DB749.html [Accessed 4 November 2011]

Gluyas, J. G., 2003, United Kingdom oil and gas fields: commemorative millennium volume. London: Geological Society.

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