SYRIA - The Geology.

Syria has a 183-km Mediterranean coastline in the north, with no petroleum discovery made offshore. But this may contain gas in the Plio-Pleistocene horizon, judging by major gas discoveries made in the south-east of the Mediterranean - off Egypt, the Gaza Strip and Israel. There is a theory, yet to be proven, that the gas-rich Plio-Pleistocene and Paleozoic formations may extend from Egypt's 180-km deep offshore economic zone up to the Aegean Sea off Turkey and Greece including areas off Lebanon and Cyprus.

Now there are talks between the governments of Cyprus, Egypt, Greece Lebanon, Syria and Turkey on possible co-operation in exploring these offshore areas. Athens recognises the issue of delineating the continental shelf in the Aegean and has called for it to be dealt with by the Int'l Court of Justice at The Hague.

The Nusayrieh (Syria) and Lebanese mountains run north-south close and parallel to the sea, bounding a narrow coast of fertile land. Prospects of finding hydrocarbons there are not encouraging. However, in the northern parts of Syria and in the south, the prospects to find oil or gas remain fairly good. As then oil minister Nader Nabulsi noted in 1993, only 35-36% of the geological structures in Syria had been drilled.

The Euphrates River runs through Syria, along a geologically important graben, from Turkey in the north-west to Iraq in the south-east. It defines the Jezira plains, including the oil-rich Deir Ez Zor, which cover one-third of the surface area and stretch eastwards to the Tigris River in Iraq.

The Jezira has proved to contain oil of high quality and gas rich in liquids. On the Iraqi side of the Jezira exploration areas, wells have yielded sweet oil.

There are two geological provinces in Syria relating to the main oil basins of the Middle East: (1) the Zagros Fold Belt to the north-east, where Syrian fairways are connected to the tectonic features of south-eastern Turkey and north-western Iraq; and (2) the Arabian Basin, the largest oil reservoir in the world, where Syrian deep sub-provinces include the Haleb Uplift (or Aleppo Uplift) and the Upper Euphrates.

A third province, known generally as the Palmyra-Lebanon-Judean Basin, underlying Syria and Jordan, is related to pre-Mesozoic developments. Above this province lies the Lebanon-Palmyrid Belt and the Euphrates graben which are a continuation of the Levant Fracture System.

The Levant Fracture System is a narrow fault of the Miocene age (Cenozoic era) extending from the Gulf of Aqaba to the foothills of the Taurus mountains in southern Turkey.

Within these three provinces, there are several trends and four major fairways defined in blocks by the government: (1) the state-owned Syrian Petroleum Co.'s fairway of producing fields to the north-east, in and around the Suwaidiyah trend of heavy/sour oils, which have structural links in north-western Iraq and south-eastern Turkey; (2) the Deir Ez Zor fairway of lighter oils in the Euphrates graben, where the main oilfields are operated by Shell which is SPC's foreign partner in Al Furat Petroleum Co.; (3) the Sham fairway of light oils in a desert near the Euphrates graben, operated by the Al Furat partner; and (4) the Palmyrid Basin of gas/condensates.

There are major shale oil deposits in several locations, mainly in the Yarmouk Valley which stretches into Jordan. Phosphate reserves in the Knneiffis region are very large, said to come next to those of Morocco which is the world's biggest phosphate exporter. There are also asphalt deposits. Various other minerals in Syria include iron ore, uranium and chromite. The country is rich in limestone, basalt and granite. The latter two make drilling for oil in many areas very difficult.

Tectonic Background: Syria lies in the western continental margin of the Arabian Plate. In pre-Mesozoic times, this Levantine margin developed along a subsidiary arm of the spreading Tethys in the north (not far from the Ionian Sea of our time) where a seaway was linked to the Indian Ocean. Several tectonic developments during the Paleozoic and great earth movements in the Early Mesozoic era brought about elevations in Syria called paleohighs.

Fragments of the Early Paleozoic caused the Rutbah and Aleppo Highs. The former was an extension of the Hail-Jawf swell of Saudi Arabia and the latter extended from the Khleissia High of Iraq.

In later times the two paleohighs were separated by the Euphrates graben in a cross-plate shear zone across Syria and Iraq. A number of subsequently mobile zones developed between these highs. A thick Palmyrid aulacogene separated the Rutbah and Aleppo highs, as well as the Sinjar trough which today extends to Iraq. A shear zone along the Euphrates, together with a trough, developed at later times.

Several major movements during the Mesozoic and Cenozoic eras introduced new tectonic features in various parts of Syria, including the Levant Fracture trending from the Gulf of Aqaba into Turkey. Among these was basaltic volcanism spread on both sides of the fracture zone during the Late Neogene and Pleistocene. A plateau of basalt developed from north-western Jordan to the Houran region in southern Syria in an area of 45,000 sq km. This is where Total of France encountered a 500-metre thick layer of black basalt before it found oil from further drilling. It is in view of such tectonic developments that geologists now are concentrating on pre-Mesozoic horizons.

The Paleozoic: There are several interesting Paleozoic sequences in Syria, as well as in Turkey, Iraq and Jordan. Important among these are the older sequences in Jordan, from Ordovician to Silurian/Devonian layers which have sourced gas and condensate. But in Syria and Iraq, there are major unconformities between the Lower and Upper Paleozoic. Some of the Upper Silurian and all of the Devonian are missing in Syria.

Only a partial section of the Carboniferous developed in the Euphrates graben and the Mesopotamian Foredeep. In Iraq, the outcrop section consisting of the Zagros mountain range exposes a good development of Ordovician sediments. But all the Silurian, most of the Devonian and a major part of the Carboniferous and Lower Permian sequences are missing. An Upper Devonian shale sequence and a Lower Carboniferous carbonate sequence have been encountered in western Iraq.

Lower Silurian shales, widely believed to have sourced the huge gas reserves of the Late Permian Khuff in the Persian Gulf, are being examined in Syria. Apart from finds in Jordan, a Devonian light oil discovery made in the 1980s in southern Turkey is said to be sourced by these shales.

Most of the Fertile Crescent (Levant) region has a favourable distribution of Silurian source rock and the potential for extensive hydrocarbon generation. The region to the west of the Jawf-Ga'ara-Khleissia axis, i.e., a major part of Syria, has good oil prospectivity because of shallow depth and relatively easy access for the drill.

The Mesozoic: An era of major tectonic movements, the Mesozoic in Syria began with a rich Triassic sequence of carbonates, mainly limestone and dolomite. Shales and evaporites developed in a succession called "Mulussa" or "Dolaa". There were also migrations from sands of the Late Permian age (close to the terminal Paleozoic). Good anhydrite seals developed, holding fairly large hydrocarbon accumulations.

Major hydrocarbon traps are found within the Triassic sequence. They consist of interbedded Mulussa carbonates, shales, and evaporites. They include the gas and condensate discoveries made by Marathon of the US in a block and adjacent areas of the Palmyrid Belt (the gas fields of Al Shaer, Cheriffe, Soukhne, etc.), as well as SPC's fields of heavy oil at the edge of the Palmyrid Basin. It is thought that the gas and condensate accumulations in the deeper part of the Palmyrid Basin are due to a greater maturity in the same source rock. The Triassic hydrocarbon occurrences of north-east Syria, north-western Iraq and south-eastern Turkey are sourced from interbedded shales in the Mesopotamian Foredeep.

Charge into many of the Triassic hydrocarbon occurrences is said to be a late event. Many of the traps in those Mesopotamian Foredeep areas were developed in the Late Neogene.

There are good evaporite seals under Syria's Triassic carbonates (reservoirs), both in the Palmyrid region and in the north-east. Oil discoveries have been made from Triassic sandstones in the east, said to be sourced from Late Permian sands.

As a result of slab-pull forces moving northwards at the beginning of the Upper Cretaceous, rifting took place in the Palmyra region and adjacent areas in Syria as well as in western Iraq. At the end of the Cretaceous, this led to collision between the Arabian Plate margin and the Bitlis-Poturge Massif in the west, and an Iranian arc in the east.

A great deal of sedimentation occurred and a number of fairly large oil reservoirs developed during that age. Most of the Syrian oil discoveries made in 1956-1979 were from these reservoirs.