The Multi-well effect
Now that we know the importance of the Initial Condition for accurate stress computation for various loading scenarios, we must look at the influences on the Final Condition. From the earlier discussions, we know that offset wells can have a thermal effect – sometimes from great distances.
The graphic shows wells that have close wellheads – from a template or in a platform. The hotter colors occur where wells are close and surrounded by others. Those that are outliers are not as hot. This prediction assumed all the wells to be identical and producing hydrocarbons at the exact same rate via identical downhole geometry and from the same reservoir. All wellpaths diverge from each other uniformly.
While the graphic indicates a simple rule, differences in geometries, production rates, water ratio, etc. can have very different effects. Wells that pass closely by another at deeper depths will also have different thermal offset effects. Wells that penetrate zones where disposal is active, or where secondary/tertiary recovery is active will likewise have variations.
The pressure profile in a producing well – points where gas is evolved or expanded, will have a Joule-Thomson cooling effect. For close wells with different flowpath geometries, the cooling will occur at different depths; these wells will have varying thermal effects upon each other. In some wells, a heating phenomenon known as a Reverse Joule-Thomson effect can also occur due to temperatures above the inversion temperature of the gas.
Evaluation of the 3D wellbore, taking into account not only the thermal history from operations on the well but also thermal effects from offset wells (and those thermal histories) is a very complicated and time-consuming process; one that requires the utmost in both thermal and stress prediction techniques, both in the software but also in the experience of those performing the analyses.
The PERIFOR amalgamation of software and the experience of Altus Engineers is the perfect solution to the problem!