The method and semi-analytical model are proposed to determine near wellbore formation heterogeneity profile distribution along horizontal wells of SAGD projects. To determine quantitative permeability distribution, temperature recovery is used, provided by systems of distributed temperature sensors installing at the horizontal wells.
Steam Assisted Gravity Drainage (SAGD) [1] is generally accepted to be one of the most effective methods of heavy oil and natural bitumen recovery. Proper management of technological parameters could increase efficiency of heavy oil recovery method in terms of cumulative oil recovery and steamoil ratio [2]. Be extremely temperature sensitive, SAGD requires thorough thermal management and proper planning. Presence of downhole distributed temperature sensors improves the steam trap control and open new possibilities for production regime optimization.
One of the keys to improve the SAGD efficiency is developing uniformly distributed steam chamber along all length of horizontal wells. This requires the knowing about reservoir heterogeneity.
At the presented work it was shown that analyzing temperature recovery during and after SAGD pre-heating phase provides information on lateral reservoir heterogeneity. To quantitative temperature data interpretation the semi analytical model was developed. The proposed model describes steam injection into porous medium filled by viscous fluid. The model developed was compared with simulation done by commercial reservoir simulation software and used for field data evaluation.
This work concerns an approximate method to estimate formation permeability distribution along the wellbore. The method requires the distributed temperature measurements being made in SAGD pre-heating process. During this stage (Figure 1) the communication is established between two horizontal wells by heating porous media. Usually this heat transfer is carried out by conductive heating, using steam circulation in both horizontal wells. The proposed method comprises the following steps: during pre-heating phase one should partially close annulus at surface thereby creating additional pressure at bottomhole. Due to pressure difference between well and reservoir steam will penetrate into oil-bearing formation. The amount of steam entered into formation (and amount of heat supplied) will depend on local permeability of formation (Figure 2). Therefore using results of temperature measurements (provided by distributed temperature sensors) during shut-in, the permeability profile along horizontal wells can be estimated.
The procedure of permeability profile evaluation could be summarized in the following:
Start pre-heating phase of SAGD process in usual manner without any changes in technology or equipment.
Partially close annulus (for creation pressure difference) to allow some portion of steam enters into formation.
Stop the re-circulation of steam after some time period of pre-heating (shut-in phase).
Carry out temperature monitoring of "shut-in" period using distributed temperature sensors.
Use the semi-analytical model of SAGD pre-heating phase to estimate permeability profile distribution along the well.
The main points and assumptions of the developed semianalytical model are following:
The model is frontal, cylindrically symmetric.
Gravity effects are not considered
Residual saturations are neglected. Initially pore space is filled by the oil.
