Enhanced Understanding of the Krechba Field, Algeria by Using Modern Processing and Depth Conversion Techniques

Krechba is one of eight fields in the In Salah Gas Development in Central Algeria, operated jointly by BP, Sonatrach and Statoil. The field is in the northern part of the acreage retained for development, and consists of reservoirs in the Carboniferous and Devonian. The Carboniferous, Tournasian C10.2 sands are the main contributor to the gas production to date, being developed for first gas in 2004. The original field discovery made in 1957 was based on 2D seismic. Due to uncertainty on the top reservoir and the thin reservoir, a 3D seismic dataset of approximately 600 km2 was acquired in 1997. Seismic amplitudes were used to define accurately the presence and quality of the estuarine sands very well developed over the field. This reservoir consists of several stacked thinner sands, at depths ranging from 2800 m to 3400 m. With this challenging task, to improve the seismic resolution and the seismic quality lead to reprocessing of the 3D volume which was finalized in 2006. This paper reviews the main steps of the seismic depth conversion process with the use of seismic velocity on this field using the reprocessed seismic, and draws some conclusions regarding the future development of the field.