Hydrocarbon identification and extraction in Rumaila oilfield

Background Introduction

The Rumaila oil field is a supergiant oil field located approximately 50 kilometers west of Basra, Iraq (Figure 1), situated in a giant anticline rich in oil and gas on the edge of the Arabian Platform. Discovered in 1953, it is one of Iraq's largest and oldest oil fields, with estimated recoverable crude oil reserves of up to 17 billion barrels, ranking as the sixth largest oil field in the world in terms of current production. As a pillar of Iraq's oil industry, the stable production of the Rumaila oil field is of vital strategic importance to Iraq's economic reconstruction and national finances.

This study utilized hyperspectral remote sensing data acquired in 2004, a critical period in the early reconstruction phase following the Iraq War. The 2003 military conflict not only resulted in direct artillery damage to oilfield production facilities but also disrupted an already fragile technical maintenance system. At this time, the Rumaila oilfield suffered from a depletion of investment due to long-term international sanctions, coupled with a severe shortage of post-war reconstruction funds. Its natural gas processing capacity was almost completely lost, and it lacked effective recovery channels and gathering and transmission pipelines, resulting in approximately 20 billion standard cubic meters of associated gas remaining unused annually. This associated gas, primarily composed of light hydrocarbons such as methane and ethane, could have been used as high-quality chemical feedstock or clean energy, but was instead forced to be directly emitted through flares burning day and night throughout the oilfield. This large-scale combustion not only caused enormous resource waste and economic losses but also generated large amounts of pollutants such as volatile hydrocarbons, sulfur dioxide, nitrogen oxides, carbon black particles, and polycyclic aromatic hydrocarbons, significantly negatively impacting the local atmospheric environment, soil ecology, and residents' health. Meanwhile, the war in 2003 further damaged existing facilities, resulting in a severe shortage of crude oil processing capacity and natural gas recovery systems. The black smoke column formed by the flare was clearly visible from tens of kilometers away. The sulfurous smell and fine particulate matter pollution in the air made the oil field area and the downwind Basra province one of the areas with the highest environmental risk in Iraq. This also provides a typical research case for remote sensing technology to monitor environmental pollution and assess ecological damage.

Figure 1 Study area

Figure 2. Cluster diagram of hydrocarbon absorption index in the study area

Methods and Principles

This article uses the hydrocarbon absorption index:

λ represents the wavelength at the location; R represents the reflectivity; and a, b, and c represent the left shoulder, trough, and right shoulder of the absorption valley, respectively. After correction, the data was extracted, and cluster analysis was performed to obtain four types of hydrocarbon absorption intensities. The hydrocarbon absorption index was used to determine the presence of hydrocarbon pollution (or the occurrence of oil sands) within the region. Figure 2 shows the overall distribution of hydrocarbon pollution in the Rumaila oilfield. It can be seen that there are two areas of strong absorption – “region a” and “region b”. Furthermore, the distribution of the medium-intensity hydrocarbon absorption index shows that the hydrocarbon-containing smoke generated by the flare combustion flows in an NNE direction.

Results Analysis

Figure 3. Cluster diagram of hydrocarbon absorption index in region a

Figure 3 is a magnified view of "Region a," a component of the northern part of the Rumaila oilfield. Areas with strong hydrocarbon absorption are located near oilfield flares and pipelines, indicating active oil and gas activity or facility leaks in these areas. Continuous venting and combustion, along with emissions during pipeline transport, lead to hydrocarbon accumulation at the surface, forming a significant hydrocarbon anomaly; the distribution is mainly NE-trending. The stronger absorption areas are primarily oil sands or previously exploited areas. Because oil sands themselves contain high residual oil saturation, and historical exploitation activities may have damaged the caprock's sealing properties, oil and gas migrate upwards and form oxidized residues at the surface, thus exhibiting enhanced hydrocarbon absorption characteristics.

Figure 4. Cluster diagram of hydrocarbon absorption index in region b

Figure 4 is a magnified view of "Region b," a component of the southern Rumaila oilfield. Areas with strong hydrocarbon absorption appear as clumps near the oilfield flares. This clump-like distribution pattern typically indicates localized, point-source hydrocarbon enrichment, possibly related to the accumulation of trace leaks due to the dense gathering and transportation pipeline network and aging facilities around the flares. It could also be oxidized residues formed on the surface after deep oil and gas migrates vertically along faults or abandoned wells. The concentrated occurrence of these anomalous patches also reflects the complex pipeline layout and dense historical production facilities in the southern development area. The stronger areas are dominated by oil sands, consistent with the long-term large-scale production in the southern Rumaila oilfield—long-term production activities have led to large amounts of oil and gas surfacing along the outer walls of well casings or induced fractures, forming oil sand outcrops rich in heavy components after long-term weathering and oxidation. The interpretation of this figure also shows that the 2003 war further damaged existing facilities, resulting in severe shortages of crude oil processing capacity and natural gas recovery systems, as well as outdated and aging environmental protection facilities.