Youssef Ibrahim
Rojava University
Qamishli, Syria
Sayed Gomaa
Tarek M. Aboul-Fotouh
Abuzeid Ali
Al-Azhar University
Cairo, Egypt
Rmelan field lies in northeastern Syria and is one of the largest oil fields in the Kurdish region. War damage has prevented Rmelan Oil Co. from extracting and preserving bottom hole oil samples for PVT analysis. Predictive PVT methods aid estimates of original oil in place and reserve calculations, but there are no correlations to predict bubble–point pressure (Pb) for Rmelan crude oil. The lack of PVT modeling, therefore, limits further exploration of the field.
To address this shortcoming, researchers at Rojava and Al-Azhar universities constructed four predictive PVT models based on Rmelan data. Two of the models used empirical correlations, and two used artificial neural networks (ANN). The models were tested against a Rmelan PVT database of 50 samples.
An ANN model offers the most accurate and reliable prediction of bubble–point pressure for Rmelan crude oils. For practical field applications, an empirical correlation can serve for preliminary estimates but will not provide the most accurate estimates for reservoir studies, production forecasting, and reserves calculation.
Rmelan field
Rmelan field lies in northeastern Syria 70 km east of Qamilshi and 30 km southwest of Al-Malikiyah–Derik. Discovered in 1958, development has made it one of the largest oil fields in the Kurdish region. The field contains an estimated 315 billion bbl of undiscovered and 69 billion bbl discovered reserves.
The war has restricted Rmelan Oil Co.’s ability to perform PVT analyses by damaging the only device in country which extracts and preserves bottom–hole crude oil samples. The lack of PVT data limits further reserve estimates and production analysis for the field.
Repairing and returning the equipment to service is unlikely, necessitating the use of alternative methods to accurately determine reservoir fluid properties. To address this situation, the current study developed new empirical and ANN-based PVT correlations for Rmelan crude oil.
Empirical correlations
Given that Pb is one of the most important PVT fluid properties, two empirical correlations focused on achieving accurate Pb predictions based on existing Rmelan data. One sample each from 50 Rmelan oil reservoirs comprise the dataset used in developing the correlations (Table 1). The data represent bubble–point pressure as a function of reservoir temperature, solution gas-oil ratio (GOR), API gravity (°API), and gas specific gravity. Collected data cover 163.57–1,472.11 psi Pb, 149–186.8 ℉. reservoir temperature, 73–420.28 scf/stb solution GOR, 26.42–43.19 °API oil gravity, and 1.05–3.60 gas specific–gravity ranges.
