Innovative Processing of 3D Land-Seismic Data
Authors: Carpenter Chris 
Published: February 2015

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 164016, ’Innovative Acquisition and Processing of Low Signal-to-Noise-Ratio 3D Land-Seismic Data Lead to a Leap in Subsurface Understanding: A Case History From Eastern Jordan,’ by Chris Pearse, Nicola Adams, Philip Bateman, Jack Bouska, Carlos Duque, Martyn Gravestock, and Johnathan Stone, BP, prepared for the 2013 SPE Middle East Unconventional Gas Conference and Exhibition, Muscat, Oman, 28-30 January. The paper has not been peer reviewed.

The Risha concession, in the desert of eastern Jordan (bordering Iraq, Syria, and Saudi Arabia) contains the partially developed Risha gas field. This has historically been a poor-seismic-data- quality area, mostly because of a complex and variably karstified near-surface region. A high-density wide-azimuth (WAZ) acquisition was carried out in a timely and cost-efficient way, allowing insights into the area’s lithology and potential fracture distribution for the first time.

Seismic Acquisition

A limited exploration and appraisal license period of up to 5 years required that BP acquire 5000 km2 of 3D-seismic data—a very large survey by onshore standards—faster and more cost-effectively than ever before. These goals would mean that BP Jordan would have to achieve production rates and costs per area typical of marine-seismic surveys.

The survey objective was to acquire a high-fold WAZ 3D survey suitable for structural interpretation, attribute analysis, and anisotropy studies. Data quality in Risha is affected by a complex near-surface region with significant karstification, causing a high degree of scattered noise that masks the primary reflection data. Previous 3D vintages were challenging to interpret; they failed to image the Ordovician reservoir adequately, were characterized by poor signal/noise ratio, and lacked resolution and continuity of key reflectors.

To overcome the challenge, 3D-survey parameters were chosen to maximize both quality and productivity. To illuminate the subsurface with a high-fold WAZ ray-path distribution, the design used a 22-live-line recording patch, with 600-m receiver-line spacing. The nominal receiver line was 27.5 km long, resulting in 12,100 traces recorded with each vibrator point (VP), using an active spread spanning from 350 to more than 490 km2. The two-way time of the targets allowed for a relatively wide receiver- line spacing so that the recording patch could sample the entire reflected wave front. Use of single line roll ensured that 11 lines were active on either side of the source swath. Implementing a single roll maximizes both the geophysical quality and the line-crew efficiency, providing full azimuth sampling, maximum surface consistency for statics, and good line-crew efficiency. Receiver groups being spaced 50 m apart with a simple linear array of six geophones was intended to further assist line-crew productivity. Source lines were positioned 50 m apart, parallel to receiver lines with a 50-m VP interval, creating both long source lines to maximize vibrator efficiency and a fully sampled source grid (50×50 m) to attenuate scattered noise and create a high-fold data set.