Steam to Oil Ratio (SOR)

Definition - What does Steam to Oil Ratio (SOR) mean?

Steam to Oil Ratio (SOR) is a measure to quantify the efficiency of production of oil from a reservoir based on steam injection into the reservoir. It can also be defined as the amount of steam injected to produce one unit volume of crude oil. SOR is inversely proportional to efficiency of steam usage which means that when the steam to oil ratio is low, more steam would be used. Thus, technology has to be improved in order to use less steam to produce equivalent amount of crude oil.

Petropedia explains Steam to Oil Ratio (SOR)

Methodologies to estimate Steam to Oil Ratio fall under Enhanced Oil Recovery (EOR) Techniques. Organizations make use of two types of steam injection techniques for the production of crude oil and both techniques have different Steam to Oil Ratio (SOR):

  • Cyclic Steam Simulation Technique (CSS) – In this technique, steam is injected into a well in a heavy oil reservoir making the heavy oil less viscous and allowing it to be produced from the same well. In this technique the Steam to Oil Ratio is three to eight (3-8). This simply means that three to eight barrels of water are converted into steam which produces one barrel of crude oil.

  • Steam Assisted Gravity Drainage Technique (SAGD) – In this technique, two horizontal wells are drilled one below the other till the oil reservoir. Steam is injected through the top horizontal well into the reservoir which heats up the heavy oil making it less viscous. With the effect of gravitational pull, the less viscous oil along with water flow down into the bottom horizontal well and are pumped to the surface. In this technique the Steam to Oil Ratio is two to five (2-5). This simply means that two to five barrels of water are converted into steam which produces one barrel of crude oil.

Since SOR efficiency is better in SAGD technique, majority of organizations make use of this EOR technique to maximize heavy oil production.

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