13 February 2018
Kindly sponsored by Gulf Keystone Petroleum Ltd
The Shaikan Field lies in the Kurdistan Region of Iraq, in the north of the country, within the Zagros fold and thrust belt. This talk describes what has been learned over the past five years of production from this giant fractured carbonate field.
The Shaikan Production Sharing Contract (PSC) was signed by Gulf Keystone Petroleum International (GKPI) in November 2007. The licence covers 280km2 and lies within the foothills of the Zagros Mountains approximately two hours by road from Erbil, the regional capital, and two hours from the Turkish border crossing to the northwest at Zakho.
The SH-1B well was drilled in 2009 and discovered oil in Cretaceous, Jurassic and Triassic fractured carbonate reservoirs. Acquisition of 3D seismic data and drilling of five appraisal wells proved a significant oil column of 800 m in the Jurassic alone, over an area covering 135 km2. The field was declared commercial in August 2012.
A Field Development Plan (FDP) was submitted to the Ministry of Natural Resources (MNR) in January 2013. Following approval in June 2013, two production facilities each of 20,000 bopd nameplate capacity were built and commissioned, and four additional wells were drilled. The field reached a production milestone of 40,000 bopd in December 2014.
Nine wells are currently on production and the field has produced over 43 million barrels to date from the Jurassic reservoirs. All production wells are flowing dry oil naturally with no free gas or water.
At the point of approval of the 2013 FDP, significant reservoir related uncertainties were recognised. These included; fracture STOIIP, vertical and lateral connectivity, fluid properties and variability, long term well deliverability, drive mechanism, aquifer influence and matrix contribution to recoverable reserves.
Continuous monitoring of downhole pressures in all of the producing wells has provided an invaluable dataset which has been used to calibrate dynamic field models and address some of the key uncertainties identified above.
An extensive programme of desktop, laboratory and field-based studies has been carried out with the aim of improving characterisation of the Shaikan reservoirs and fluids. This knowledge has been brought together in a series of discrete fracture network sector models which have been calibrated to single well drill stem and production tests, multi-well interference tests and long-term production data.
Calibration of these models to the five years of Shaikan production history has provided an understanding of the drive mechanism for the Jurassic reservoirs and provided confidence in the estimation of connected STOIIP, fluid properties and future well performance.
With 43 million barrels of oil produced to date, Shaikan has produced only 8% of its estimated 2P Jurassic recoverable reserves 1. A programme of investment is planned which is aimed at maintaining Jurassic production in the short term with further expansion in the medium to long term.
1 2P Jurassic Reserves 568 MMbls – December 2016 ERC Equipoise Reserves Support Letter
Plans to develop the Triassic reservoirs are under investigation and the Cretaceous could yield additional, as yet commercially unproven resource potential.
Although Shaikan is in the infancy of its production life, the lessons that have been learned during this early phase of development provide a valuable foundation upon which to build future expansion phases.
These materials are presented by kind permission of the Ministry of Natural Resources (MNR) of the Kurdistan Regional Government (KRG). We also would like to thank our partner MOL for their support.
The Geological Society of London
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