The Kurdistan Region of Iraq has witnessed extraordinary levels of exploration activity since the first exploration well to be drilled in over two decades was spudded in 2005. Since then almost 200 wells have been drilled encountering recoverable reserves estimated to be in excess of 15 billion barrels of oil equivalent. Whilst the region is in close proximity to many of the giant and supergiant fields of Iran and Iraq, the reservoirs in which discoveries have been made are largely different. In Iraq a large percentage of discovered reserves reside in Cenozoic and Cretaceous sediments capped by Cenozoic evaporite sequences. Over much of Kurdistan, particularly the north and northeastern parts of the region, Cenozoic strata are absent.
A decade ago many were doubtful that significant quantities of hydrocarbons could be trapped in the absence of the Cenozoic evaporite sequences. Furthermore, whilst the presence of large surface structures and significant oil seeps were encouraging to some, to others it fueled concerns about trap leakage. Today the majority of the surface anticlinal features in Kurdistan have been drilled, but remain to be fully evaluated. Almost all of the exploration activity in Kurdistan has taken place on 2-D seismic with vertical exploration wells. In the last few years, a number of 3-D seismic surveys have been acquired and these will undoubtedly lead to production and reserve enhancements in parallel with increased subsurface complexity.
Following a decade of exploration, three fields have been fully appraised and have a reasonable early production history: Tawke, Taq Taq and Khurmala. Reserve additions in the Tawke Field have been significant as a result of increased production performance due to better than originally anticipated reservoir properties, better pressure communication and additional reserves found in older reservoirs. It is probable that similar trends will occur in other fields and discoveries.
Whilst a small number of horizontal wells have been drilled, advanced techniques used for producing from tight fractured carbonates such as multilateral wells, hydraulic fracturing, selective completions, proping and water injection have not as yet been used in the region. Almost all wells in Kurdistan have been drilled on surface or near subsurface structures within the foreland or the fold belt. Some wells have drilled through thrusts, more often by accident as opposed to on purpose. There have been virtually no dedicated wells for pure sub-thrust plays or stratigraphic traps although hydrocarbons have been found below significant thrusts and also beyond apparent structural closure in some structures.
Challenges remain in what is a structurally complex and recently deformed region. High levels of exploration and appraisal activity persist and new pipeline infrastructure is under construction. It is likely that the Kurdistan Region of Iraq will develop to become an important contributor to world oil and gas production. This paper aims to summarise the first decade of exploration and appraisal activity in Kurdistan Region of northern Iraq. Due to the paucity of technical papers on this subject, this document draws upon the authors’ own knowledge and material published by companies operating in the region.
INTRODUCTION
This paper is considered to be the first to provide a comprehensive review of exploration, appraisal and production activities in Kurdistan Region of Iraq (Kurdistan) since the region ‘opened’ in 2003. Kurdistan has become one of the most active onshore hydrocarbon provinces in the world with production rising to over 400,000 bopd (barrels of oil per day) and newly discovered reserves in excess of 15 billion barrels.
The paper reviews the licensing and exploration activity since 2003. It details some of the challenges of drilling in this emerging fold-and-thrust belt. A suite of maps document all the key discoveries and producing fields and also detail wells that have been unsuccessful with possible reasons for their failure. The paper concludes with a summary of current activity and future trends, which are likely to shape Kurdistan over the next decade.
There are few technical publications specific to Kurdistan and much of the material in this paper is drawn from published competent persons reports and corporate presentations, some of which are no longer available. It is hoped that this paper will provide a useful summary of the first full decade of exploration activities in the Kurdish region.
LICENSING AND EXPLORATION ACTIVITY IN KURDISTAN
Activity Prior to 2003
The first exploration well in the Middle East was drilled in 1901 on the Chia Surkh structure close to the present-day border with Iran in the southeastern part of Kurdistan (Figure 1). The well was located on a hill close to an active oil seep and it was abandoned with oil shows after drilling to 710 m in depth. Between 1905 and 1922 four more wells were drilled on the structure, some finding oil shows with none of them drilling below 800 m (Aqrawi et al., 2010). During the next 83 years (1922–2005) less than 30 wells were drilled in Kurdistan and these only targeted seven structures; Chia Surkh, Pulkhana, Kor Mor, Khurmala Dome, Chemchemal, Taq Taq, Demir Dagh and Jabal Kand (Figure 2).
During this same period a number of significant discoveries were made both in the central part of Iraq and in the Zagros of Iran. The first significant discovery in the Middle East was made in 1908 at Masjid-i-Suleiman in the Zagros of Iran (Sorkhabi, 2008; Figure 1). The Kirkuk Field was discovered in 1927 by the Turkish Petroleum Company (later to become the Iraq Petroleum Company, IPC). The discovery well (Baba Gurgur-1) encountered oil in the Cenozoic and blew out, taking a number of days to control. The discovery well was located on a surface anticline and close to a natural gas seep: “The Eternal Fire of Baba Gurgur” (father of fire), which is believed to have been active for more than 4,000 years. Some of the other discoveries in Iraq include: Qaiyarah (1928), Rumaila (1953), West Qurna (1973), Majnoon (1975), East Baghdad (1976) (Figure 1). The Khurmala Dome, at the northwestern end of Kirkuk, was first drilled pre-second World War but it was plugged and abandoned, along with other wells, as European troops approached Egypt in the early 1940s. During the Iran-Iraq war (1980–1988) exploration and appraisal drilling continued in Iraq, albeit at a much reduced pace. A comprehensive summary of the history of oil exploration in Iraq is given in Aqrawi et al. (2010).
The Taq Taq structure in the central part of the Kurdistan Region of Iraq (Figure 2) was first drilled in 1960 and drilling was suspended in April 1961 after setting 95/8 inch casing in the top of the Upper Cretaceous Shiranish Formation. This followed the issuance of Public Law 80, which took away 99.5% of the IPC’s ownership (Falola and Genova, 2005). In 1964, the government established the state-owned Iraq National Oil Company (INOC) to develop the concession areas taken over from IPC. Sixteen years later in 1978, INOC decided to re-enter the Taq Taq-1 Well and it was deepened to the Lower Jurassic, testing oil from a number of formations within the Cretaceous. In 1979–1980, INOC contracted a rig to drill more wells on the discovery (Taq Taq-2 discovered oil in the Eocene Pila Spi Formation), but tensions between the Kurds and the Baath regime, coupled with the outbreak of the Iran-Iraq war, led to a cessation of drilling. In 1994, the Kurdistan Regional Government (KRG) tested and completed Taq Taq-1 and Taq Taq-2 signalling the first production from Kurdistan. Prior to the Iraq War of 2003, the Turkish company Genel Enerji AS signed the first production sharing agreement in Kurdistan (KRG, 2002). This contract was for the Taq Taq Field. Soon after another Turkish company, Petoil Petroleum, together with US-based Prime Natural Resources were allocated areas to explore (KRG, 2003). These contracts signalled the start of a new phase of exploration activity in Kurdistan.
Following the Iraq War in 2003, more international oil companies started to approach the KRG and undertake technical work in the Kurdish autonomous region. At this time, neither the Constitution of Iraq nor the Oil Law had been passed and there were ongoing disputes regarding revenue sharing between the KRG and the Iraqi Central Government (ICG). The Kurdish Ministry of Natural Resources (MNR), which at this stage comprised only a handful of people, drew up a ‘block map’ of the region nominally assigning one surface structure per block. The 48 blocks were ranked into low, mid and high risk and fiscal terms varied to reflect perceived technical risk. In addition, 8 lettered blocks were delineated along the border with Turkey and Iran (Figure 2).
In addition to the political risk, there was a paucity of subsurface technical data specific to Kurdistan and no service sector. Prior to the Iraq War in 2003, very few exploration wells had been drilled in Kurdistan (Figure 2). There was virtually no seismic data, and what wells and seismic data were available, avoided the more mountainous areas and were generally close to the existing Iraqi oil fields. Moreover, even if one knew of the possible existence of subsurface data, getting access to it was often extremely difficult.
The Iraq Lexicon (van Bellen et al., 1959-2005) has proven to be an invaluable source of data on the lithostratigraphy of Iraq, incorporating four decades of field surveys and investigations. Local geologists and students have produced theses on the surface structure, stratigraphy and hydrogeology. Whilst providing a rich source of information, in the absence of an oil industry, there had been little focus on petroleum systems and what little data was available needed extrapolation into the subsurface.