Abstarct: Pore pressure is known as the fluid pressure inside porous rock, which is an important parameter in geomechanical modeling. The accuracy in predicting the pore pressure causes the optimal mud weight and heel points of the casing pipes picked up appropriately. Therefore, correct estimation of pore pressure while increasing safety in preventing the collapse of the borehole, has an effective role in cost optimization and economic drilling. Gachsaran Formation is one of the most important formations in the oil-rich regions of southern Iran, which acts as a caprock for the Asmari Formation. Due to the special geomechanical and lithological conditions, estimation and preparation of the compression model in the formation has always been challenging. In this research, by using petrophysical logs, geological information, VSP and drilling parameters in 3 wells of Aghajari and Maroon oil fields, a compression model by various relationships for Gachsaran Formation is presented. Initially, the mechanism of high-pressure induction was investigated using velocity vs. density data, which indicates the existence of unbalanced consolidation as the main mechanism of high-pressure induction in the studied fields. According to the identified mechanism, the pore pressure was calculated from Eaton analytical methods and the simple form of Bowers method as well as the estimation method baxsed on Eaton drilling parameters and the results of the mentioned methods were validated by mud weight and evidences and drilling reports. Finally, MATLAB programming language and related codes of the data fusion methods were used to combine the results of pressure estimation in different ways to achieve a desirable and extended respond. The results showed that the Eaton method can be used in Maroon field with an exponential constant of 2.2 and in Aghajari field with an exponential constant of 1.5. Also, the results of the data fusion methods show the priority of Eaton method, then Eaton drilling parameters method and finally Bowers method in Maroon field