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In-situ stress analysis using image logs

MostafaAlizadeh, ZohrehMovahed, Radzuan Bin Junin

In the reservoirs, rocks are affected by three principal stresses (ó1=maximum principal stress, ó2=intermediate principal stress and ó3=minimum principal stress) due to the overlying strata and tectonic region, but drilling a new well will create in-situ stresses (óhmax=maximum horizontal in-situ stress, óhint=intermediate horizontal in-situ stress and óhmin=minimum horizontal in-situ stress) that will disrupt the stress system in area around the well.Analyzing this newset of stresses is very important, because during the new drilling operation the rock strength around the well will be changed that can affect the other drilling operations and also the other operations, such as hydraulic fracturing, EOR mechanisms, and so on. In this paper, we will find the in-situ stresses direction in Gachsaran field, and also by doing this case study and showing the appropriate examples of log interpretation, we will introduce this technology. This job shows that the maximum horizontal in-situ stress direction of this field is NE-SW, and the minimum horizontal in-situ stress direction is NW-SE; for two wells in this field, the direction of in-situ stresses are quite different from the other wells that it might be the effect of fault, fold and diapirism on in-situ stresses.