( A little knowledge in the field of  petroleum engineering effects the Industry)

Dr. NANI

 By: Dr. Abdul Sattar Othman Nani.

 Scientific advisor to the PEPA Chairman.

       e.mail: golsha2004@yahoo.co.in

                    ASNANI@y.net.ye.

Introduction.

In the beginning of last century few geological activities were performed by some of Geological Survey and Petroleum companies, the main idea was to construct Stratigraphy and Tectonic picture of Yemen.

In the early sixties and seventies of the last century, scattered exploration activities took place in Yemen ( Red Sea, North Hadramaut-Mahra and Gulf of Aden ). During this phase very few hydrocarbon occurrences were detected but not commercial discoveries because of the immature exploration knowledge and experience ( Very poor picture of the Tectonic which in turn had severe effect on the Basin analysis ).

In 1984 Hunt had the first discovery in the Marib Sub-basin and subsequent discovery in the Shabwa Sub-basin achieved in Ayad Block-4 by the Soviet Techno-Export. They had demonstrated  the presence of a Jurassic Rift Basin in the Marib-Shabwa-Hajar region. In 1990 Canadian OXY had the first discovery in the Seyun- Masila Basin.

Yemen had a big booming of the oil companies in the early Nineties due to the Birth of the Yemeni Unity on 22-May-1990. The following oil companies( BP, Shell, Chevron, Amoco, British Gas, Sun Oil , BHP and others) arrived and performed the exploration activities in different Blocks.

*Scientific reasons for the success of the oil companies.

The main reasons are as follow:

1-    A sound knowledge of the Petroleum Geology of Yemen.

2-    An excellent coordination between the Geologists and the Geophysists during the exploration phase.

3-    Had a thorough understanding of the tectonic of the Block.

4-    Very familiar with the sedimentary Basins in Yemen and the surrounding adjacent countries.

5-    Utilized right exploration tools during the exploration phase.

6-     Excellent exploration program.

*Why some of the oil companies failed in some of the Blocks, while others achieved hydrocarbon discoveries in the same Block.

( From the mistakes of others we learn) Dr.Nani 

1-    Weak exploration team. Means neither having Geological nor having Geophysical back ground.

2-    Poor exploration program, especially having economized seismic program, where the spacing between the seismic lines is very big, this in turn could miss small structures.

3-    Bad quality of seismic which has a very big effect on the seismic interpretation. Sometimes there might be no structures but the poor Geophysists  draw  faults and make beautiful Horst type of structures, when there isn’t any structure in reality. A good example was in Jiza-Qamar Basin.

4-    Poor Geological interpretation. Unfortunately some of the Petroleum Geologists watch clearly on the seismic lines Breaching, but still want to drill ( this leads to a dry hole ). Mostly in the Sayun-Masila Basin.

5-    Sometimes it is crystal clear that some of the oil companies locate the well having only one seismic line!!!! This is still a Lead and not a Prospect because still we don’t have the four-way closure.

6-    Improper or false test results could lead to a wrong evaluation of the Block from the point of view of its hydrocarbon potentiality.

7-    Qishn Clastics  “ Fashion “. This fashion began as soon as excellent discoveries were achieved by Nexen in the Sayun Masila Basin in the Qishn Clastics. Unfortunately some of the oil companies are still continuing utilizing it even in the other Basins. This proves lack of good understanding of the Stratigraphy of their block. This in turn will lead to plenty of dry holes.

8-    Big but rare mistake is done by the Geologists and Geopgysists, when mis-interpreting between the Rays mem (Carbonates) and Qishn Carbonates in the Sayun-Masila Basin. It is very important to note that:

a-    Rays mem is local and under it lies Lower Harshiyat Calstics.

b-    Qishn Carbonates mem is a regional seal and directly below it lies the Red Shale and under this later lies the main reservoir Qishn Clastics.

c-     What was mis-interpreted in Block- R2, when the well Dawan-1 was drilled is as follow:

1-    The Rays mem was considered as Qishn Carbonates!!!!!!!!!

2-    The Lower Harshiyat was considered as Qishn Clastics !!!!!!!!!

3-    Therefore where has gone the Red Shale, which comes before the Qishn Clastics ????.

4-     It is very important to note that Qishn Caborbonates has a distinctive Foraminifera  fossil called Choffatella decipiens, which is not present in the Rays mem.

Rays mem surface section is present in the Jabal Shabb, Jabal ar Rays, Jabal Billum. It is easily picked-up on the seismic sections.

Conclusion.

1-    Right exploration tools could lead to successful results.

2-    Big oil companies search for big fishes ( Oil reserves more than 500 million barrels).Therefore it is better to look for medium and small size oil companies. Some of these oil companies have good results in Yemen.

3-    Sound knowledge of the Yemeni Basins is extremely important.

4-    Excellent coordination between the Geologists and Geophysists is a

must.

Recommendations.

1-    It is time for the exploration and production activities to introduce soft wares in different disciplines for the Scientific Research work.

2-    The oil companies should not neglect to optimize seismic

static’s corrections and depth conversions in order to accurately image the subsurface structural traps. Such kind of neglect would hinder the Reserves Calculations.

3-    Poor signal to noise ratio from numerous canyon walls and

“ Fault Shadow “ velocity anomalies overlying many of the tilted block culminations. This could lead to dry holes. Therefore during Processing and Interpretation of seismic data a necessary effort should be applied.

4-    A team of highly field experienced Petroleum Engineers

should control and revise the work programs performed by the oil companies during the exploration phases.

   6/8/2006