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

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.