Sub-Surface Investigation of Khashim Al-Ahmer Gas Field Using Seismic Reflection Data

Abstract

This paper is carried out to detect the subsurface structures that have geological
and economical importance by interpreting the available reflection seismic data of
an area estimated to be about (740) km2. The Khashim Al-Ahmer structure is partial
of series structures of (Injana – Khashim Al-Ahmer – Mannsorya) from the (NW to
the SE), it is located within for deep faulted area. The component of the one
elongated dome of asymmetrical of structure which has(SW) limb more steeper than
the (NE) limb.Twenty three seismic sections had been interpreted for two seismic
surveys and the total length of all seismic lines is about (414.7) Km. Interpretation
of seismic data was focused on two reflectors (Fatha and Jeribi) Formations which
belong to Lower and Middle Miocene age. The reflectors were picked and identified
by tying them directly to well Khashim Al-Ahmer-2, the Lower Fars(Fatha
Formation) reflector was picked at TWT ranging from (0.3-1.7) sec while the Jeribi
reflector was picked at TWT ranging from (0.83- 2) sec. The depth map showed that
the depth of the Jeribi Formation ranges between (1100 - 2000) m, and the velocity
maps of studied reflector showed increase of velocity values to the south east and
there is a local closure in the north east of the study area and decrease to the north
west and the velocity values decrease and give closure situated below well KA-
2.The magnitude of velocity values ranges in Jeribi velocity map from (3100 to 3400
m/sec). Seismic attributes techniques (instantaneous phase) is important to detect the
hydrocarbon accumulation on seismic sections. Major faults (reverse and thrust)
were picked along study area on instantaneous phase sections. These faults extend in
NW-SE trend and the displacement of the fault ranges between (400-660) m. The
velocity, time and depth maps were drawn by the aid of GeoFrame and petrel
software.