Effects of Water Coning on the Performance of Vertical and Horizontal Wells-A Reservoir Simulation Study of Hassi R'mel Field, Algeria

Abstract

Generalized empirical correlations have been developed to predict, (1) critical oil rate, and (2) water breakthrough time in vertical and horizontal wells. Water coning is a serious problem in many producer wells, which increases the cost of producing operations, and reduces the efficiency of the depletion mechanism and the overall recovery. A numerical simulation was used to analyze the most relevant fluid and reservoir parameters that affect water coning using a 3-D radial vertical well model and a 3-D Cartesian horizontal well model. The method of determining the average oil column height below perforations at breakthrough (hwb), was developed from a stepwise procedure. First, a number of simulation runs was made to investigate the coning performance at different reservoir and fluid properties for both vertical and horizontal wells. Then, for each simulation run, water oil ratio (WOR) was plotted against of average oil column height below perforations (hbp), on a semi-log scale, from which (hwb) was determined. Once the (hwb) data was obtained for all the simulation runs, regression analysis was then used to define the relationship between (hwb) and various reservoir and fluid properties. An extensive parametric sensitivity analysis of water coning was made to provide data for developing a predictive correlation of calculating breakthrough time and breakthrough height as a function of various reservoir and fluid properties. The simulation outputs are used to develop empirical water coning correlations to predict critical oil rate, and water breakthrough time for vertical and horizontal wells. The parameters were grouped together based on the basic flow equations and the grouping was confirmed by regression analysis. Several field examples from CTH1 area of Hassi R'mel field in Algeria will be discussed. Introduction Water and gas coning are serious problems in many oil field applications, where the production of water and gas from a thin oil reservoir is a common occurrence, which increases the cost of producing operations, and reduces the efficiency of the depletion mechanism and the overall recovery. We will deal with one cause of this production namely, coning. One of the main reasons for coning is pressure drawdown. A vertical well exhibits a large pressure drawdown near the wellbore, whereas horizontal well exhibits minimum pressure drawdown, thus horizontal wells provide option whereby pressure drawdown can be minimized, coning tendencies can be minimized, and high oil production rates can be achieved. Two forces control the mechanism of water coning:dynamic flow force (applied force), andgravity force. In water-coning systems, the upward dynamic force due to wellbore drawdown causes water at the bottom of the oil zone to rise to a certain height at which the dynamic force is balanced by the weight of water beneath this point. As the radial distance from the wellbore increases, pressure drawdown and upward dynamic force caused by it decrease, and the height of the balance-point decreases along the radial direction. Therefore, the locus of the balance point is a stable cone-shaped water oil interface. Oil flows above the interface, while water remains stationary below the interface. As the production rate is increased, the height of the cone above the original oil-water contact also increases, until at a certain production rate, the cone becomes unstable and water is produced into the well.

Integrated-reservoir-model-based critical oil rate correlation for vertical wells in thin oil rim reservoirs in the Niger Delta

“…Note, in Figure 2, this actual critical oil rate (qc) is the highest (apex) oil production rate at which the water-cut begins to increase, thus, indicating water breakthrough. Other authors': Hoyland et al [14] and Recham et al [15] correlations predicted critical oil rate of 33.76 bbl/day and 75.19 bbl/day respectively, for the ADX Oilfield. These authors' correlation predictions were far less than the actual critical oil rate of the ADX Oilfield in the Niger Delta.…”

“…In the literature, Hoyland et al [14] and Recham et al [15] had developed critical oil rate (qc) correlations from numerical approach. These correlations basically comprises of the fluid density difference (∆ρ), fractional well penetration (hp/h), horizontal permeability (kh), oil column (h) and drainage radius (re).…”

“…These correlations basically comprises of the fluid density difference (∆ρ), fractional well penetration (hp/h), horizontal permeability (kh), oil column (h) and drainage radius (re). On the other hand, Recham et al [15] added oil viscosity (µo), oil formation volume factor (Bo) and dimensionless critical rate ( D c q ) to the aforementioned parameters. The dimensionless critical rate ( D c q ) contains mobility ration (M), anisotropy (kv/kh), height above perforation -oil column (hap/h) and height below perforation -oil column (hbp/h) terms.…”

“…The dimensionless critical rate ( D c q ) contains mobility ration (M), anisotropy (kv/kh), height above perforation -oil column (hap/h) and height below perforation -oil column (hbp/h) terms. Hence, the Hoyland et al [14] and Recham et al [15] correlations are expanded in Equations 1 and 2, respectively.…”

“…From this, the developed critical oil rate correlation is expanded in Equation 14. Then, the developed correlation was validated by comparing its prediction alongside with other authors: Hoyland et al [14] and Recham et al [15] correlations with the actual ADX Oilfield critical oil rate; as obtained from the production history data. Also, sensitivity studies of the completion interval parameters: fractional well penetration (hp/h) and height below perforation -oil column (hbp/h) on the critical oil rate (qc) were performed using the ADX reservoir model (Figure 1).…”