Comparative evaluation of productivity indicators in carbonate reservoir modeling by a case study for the Mishrif Formation in the Iraqi Buzurgan Oilfield

Valid projection of Well productivity is essential for carrying out appropriate criteria and to avoid increasing the cost of exploration and development. A combination of various reservoir evaluation procedures can be beneficial to estimate Well productivity according to different data, including seismic, mud logging, well logging, well-testing, formation test data, etc. In this study, the productivity index was extracted based on well logging and well-testing by Interactive Petrophysics and Saphir™ to comprehend reservoir productivity behavior and be a valuable guide for planning future drilling processes. The results indicated that the correlation between the J-predicted and productivity index (PI) results from the well-logs interpretation is power law in the northern part of the field and linear in the south. The average porosity values in the southern part of the Buzurgan field are lower than in the north and the average water saturation and permeability in the south are slightly higher than in the north. On the other hand, the Multiple Linear Regression (MLR) analysis for PI identifier and PI by well-logging and Well-testing shows that the southern part of the field has a better PI than the north. The MB21 was the best unit in the Mishrif reservoir in the field. Likewise, the oil reserve in the south of the field is higher than in the north due to the Net-to-Gross and bulk volume results, especially in zone 5, representing the MB21 unit. In addition, the water saturation model shows that the oil–water contact (OWC) is at a depth of − 3877 m in the south part and 3885 m in the north. By examining the Well performance using the Ecrin program, the Productivity Index of layer MB21 is equal to 6.3 in the south and 5.9 in the north. Finally, the volume of the Oil initially in place (STOIIP) for the Mishrif Formation is estimated to be approximately 4138.7 million barrels.