Patent ID: 9482081
Filing Date: 2016-11-01
CPC Classification: E21B

Claim Text:
1. A method for preheating an oil reservoir, the method comprising: injecting a saturated or a superheated steam at an initial injection pressure during an initial preheating stage of a steam assisted gravity drainage (SAGD) process, wherein the steam is injected into a tubing disposed within a well traversing the oil reservoir, measuring temperature at an outlet of the tubing during the initial preheating stage of the steam assisted gravity drainage process, the temperature is measured by at least one temperature sensor installed at the outlet of the tubing, calculating a heat flow from the well to the oil reservoir using the temperature measured at the outlet of the tubing during the preheating initial stage of the steam assisted gravity drainage process and reservoir thermal properties, calculating an optimal steam injection rate corresponding to a moment when steam quality of the injected steam at the tubing outlet becomes greater than zero, wherein the optimal steam infection rate W(t) is calculated according to: where Q(t) is the calculated heat flow from the well to the oil reservoir, L is a specific heat of steam condensation, ΔX=X 0 −X 1 , X 0 is steam quality at an inlet of the tubing, and X 1 is steam quality at the outlet of the tubing, and decreasing a steam injection rate to the calculated optimal steam injection rate value by decreasing the initial injection pressure to a value providing the calculated optimal steam injection rate value and constant temperature at the outlet of the tubing.