A Comparative Laboratory Analysis of Steamflooding With Horizontal Wells In Heavy Oil Reservoirs With Bottom Water Zone
Authors: Bagci S. , Aybak T. , Shamsul A. 
Published: March 2010

Abstract
Two laboratory 3D scaled models were developed to compare the performance of steam flooding in reservoirs having bottom water zone with the application of different well configurations. One of the models was triangular, designed to represent 1/12th of a 7-spot pattern and the other was a square that corresponds to ?th of a 5-spot pattern in the B. Kozluca field in Turkey. Nine experiments were conducted by using the triangular model with or without bottom water zone, whereas four experiments were conducted with the rectangular model. The well configurations were changed during the course of experiments to determine their effects on oil recovery. Bottom water thicknesses were changed to see the effects on oil recovery. The physical properties of crushed limestone and crude oil (12.4 ° API) mixture were kept constant during the experiments. Steam was injected through a vertical injection well in both models. Strings of thermocouples were used to observe 3D temperature distribution inside the models.
The maximum oil recoveries were obtained by placing the horizontal producers along the hypotenuse of the triangular model and the diagonal of the rectangular model, respectively. Besides, in both cases, the same well configuration provided better oil recovery than any other well configurations even in the presence of a bottom water zone. Oil recoveries decreased with increase in the thickness of the bottom water zone. SOR increased in the presence of bottom water.

Introduction
The increasing demand of non-renewable fossil fuel energy and the gradual depletion of conventional crude oil reservoirs led to the development of heavy oil reservoirs. The most efficient means to recover oil from these heavy oil reservoirs is thermal recovery method in which heat is applied to the reservoir. The application of heat in the form of hot water, hot gases, and steam reduces the viscosity of these heavy oils upon which, a more economic recovery is readily obtainable.
These days, the thermal recovery method is widely known and applied worldwide for secondary and tertiary recoveries. Of all the thermal recovery methods, steam injection is the most popular method. Following steam injection into any heavy oil reservoir, the viscosity, specific gravity and flow resistance of the fluid in the reservoir changes, resulting in oil production increases. The reduction in the viscosity as a result of an increase in the temperature, facilitates the movement of the heavy oil.

Advantages of Horizontal Wells
Because of their numerous advantages, horizontal wells have gained attention in the petroleum industry(1,2).Horizontal wells provide larger contact within a reservoir and hence, eliminate the need for multiple vertical wells to acquire same reservoir drainage. Recovery is two to five times greater than that of a non-stimulated vertical well.In the case of a reservoir where vertical penetration of the formations would be uneconomical, drilling of the horizontal well would render a sufficient well bore opening and a possibility of a more economic recovery.Horizontal wells in the reservoir where coning of water and gas are predominant provide a better oil recovery while minimizing the coning effects.