Significant Impact of Non H-C Gases (NHG) on Reservoir Fluid of a Jurassic, HPHT and Tight Carbonate Discovery in North of Kuwait: A Case Study of a Sour and Critical Fluid Characteristics and Fluid Compartmentalization
Authors: Al-Dousari Sara , Al-Bader Haifa , Al-Otaibi Ahmed , Al-Shuaib Sara , Chakrabarti Bahaskar 
Published: March 2023

The objective of this paper is to show the effect of non-HC gases NHG on critical fluid characterization of HPHT discovered deep Jurassic reservoir in north Kuwait in addition to Fluid characterization and compartmentalization with objective of assessing HC potential, well deliverability and reservoir fluid & rock characteristics.

Jurassic reservoirs in the state of Kuwait are deep and tight with High-Pressure and High-Temperature (HPHT) environment. The discovery well was drilled targeting the Marrat formation to prove hydrocarbon in this area. The well was successfully completed & tested and then a complete set of surface & subsurface data was acquired including production measurements and downhole P/T gauge data. The produced fluid was found highly sour and of critical-nature Therefore, a detailed fluid characterization process plus a fully-integrated G&G and Engineering analyses were performed to distinguish the fluid nature whether it is Volatile Oil or Gas Condensate and to prove reservoir and fluid compartmentalization using multiple PVT experiments and different analog wells from North Kuwait. Moreover, historical reservoir pressure and well performance for all the wells in this field were tracked and analyzed as t the discovered well was followed with an intensive appraisal campaign with variance in reservoir/fluids characteristics with objective of assessing HC potential for further Development plan to support achieving the strategic production targets. The four wells connected to one of Jurassic Facilities and ready for further development.

By integrating both reservoir and fluid analysis, The Northern part observed better reservoir quality and production performance, while reservoir layers are thinning toward the southern part of the structure with the appearance of organic content. The PVT depletion experiments along with compositional analysis and phase envelop all indicated reservoir fluid type is Volatile oil, where saturation pressure is sensitive to reservoir temperature and percentage of non-hydrocarbon gases H2S & CO2. As a result, the fluid found to be highly volatile oil with very high GOR. Fluid compartmentalization is also observed in this field between the three wells as the fluids were lighter towards the south, which will be confirmed after testing the fourth well that was initially drilled to prove the structure boundary/extension.

Tremendous exploration efforts and activities resulted in remarkable Jurassic light oil discovery with substantial addition of proven reserves and commercial production potential, which will definitely support achieving the strategic production targets. The exploratory and appraisal wells are currently connected to one of Kuwait's Jurassic facilities handling high concentrations of H2S. After the completion of exploration campaign and completing the fully-Integrated Engineering analyses the reservoir is ready to be transferred to the Hosting Field development.