The integration of precise geochemical analyses with quantitative engineering modeling into an interactive GIS system allows for a sophisticated and efficient method of reservoir characterization. This project emphasizes the integration of engineering with geology via the use of Geographic Information Systems in order to provide successful solutions to oilfield operations. The study area is the Mahala oil field in the Los Angeles basin of Southern California. Primary datasets include concentrations and isotopic ratios of the noble gases (He, Ne, Ar, Kr and Xe) as well as electrical logs (spontaneous potential, resistivity) in addition to complementary field data (CH4, BaSO4, SO2, rates, saturations). Produced fluids are sampled from active wellheads and analyzed for their geochemical characteristics. Electrical well logs are inputted into modeling software and used to generate a geological model. Reservoir properties and field variables are formulated into a reservoir simulator and subsequently parameterized and integrated along with production data into an objective function. Techniques utilized include mass spectrometry, geostatsitical cokriging and cosimulation, numerical modeling as well as inverse modeling. Results will provide useful insight on reservoir history, properties and expected behavior, which provides assistance for formation evaluation, detection of pay zones as well as determination of the field continuity and interaction of fluids. Information obtained will be used to make informed decisions such as drilling, perforating or enhanced oil recovery. This case study will demonstrate the effectiveness of combining GIS-assisted engineering tools with petroleum geology.