In enhanced oil recovery, high frequency electromagnetic waves are used to heat the oil reservoir and for this purpose an antenna is inserted in a borehole close to the production well. It requires a large numbers of boreholes for the antenna to get uniform heating. In case of offshore these problem can be avoided if a horizontal antenna is towed close to the seabed which maximize the electromagnetic energy transferred from the overburden to reservoir. For this purpose new twin collinear dipole antenna with a total length equal to one wavelength is designed and full scale modeling in offshore environment was done by using computer simulation technology (CST) software. Electromagnetic response of oil reservoir by using new antenna is studied for a model consisting of a 100 m thick oil reservoir having resistivity of 100 ohm-m, buried at a depth of 1000m in overburden with 1000m seawater. It was observed that new antenna gave 365 higher electric field than half wavelength dipole antenna at the far source receiver offset. At the target depth of 2500m new antenna gave 336 more electric field magnitude as compared to half wavelength antenna. In the response of different frequencies of new antenna, electric field value 8.18E -07 V/m at low frequency (0.125Hz) is more than 5.79E-42 V/m at frequency (10KHz). Magnetic field value 5.81E-05 A/m at low frequency (0.125Hz) is more than 1.74E-39 A/m at frequency (10KHz). It was investigated twin collinear dipole antenna produced stronger electric and magnetic fields as compared to half wavelength dipole antenna in offshore environment. © 2012 American Institute of Physics.