ICE 2022


Historical production behaviors from some wells, it is evident that the conventional geological interpretation is not enough to reproduce the dynamic behavior of the reservoir. Some producing wells in Eocene manifests a wide range of production decline, from 1 to higher than 25% per month, which many times is nor predicted. Seismic data, well logs, cores, fluids, and reservoir pressure measurements from 5 oil Eocene fields. In order of scales, seismic data was used for areal distribution and subdivision of 1 to 3 units consistent with the correlative major lithologic units in the wells. Cores and drill cuttings samples from 50 wells helped to recognize units equivalent to the Bouma sequence with their respective lithological features and sedimentary structures in carbonate rocks, the microscopic explanation is reinforced with the particle sizes ranging. Within each major lithologic unit recognized with well logs, cyclicity in the sequences was observed. Eventually within the cycles there is gradation from calcirudites to calcarenites and back to massive calciruditas, this is due to the influence of energy peaks during sedimentary transport. Interrupted sequences were also identified due to abrupt loss of energy with the consequent deposition of fine sediments. Once the sedimentary units and volumetric trends were characterized, the diagenetic events with high impact on hydrocarbon production were analyzed. Sedimentary patterns, diagenetic features, wellbore pressure measurements, capillary pressures and pore throat analysis, were articulated to assess those characteristics of the pore system that are favorable to oil storage and flow. In addition, qualitative analyses of oil content in rock samples were performed and their relationship with the intervals where porosity tends to be lost, to understand the causes and conditions of occurrence of these events, and consequently explain the productivity of wells. With the results of this study, it was possible to give a geological explanation of the production behaviors of wells that were tested, and guide future production priorities based on: 1) Thicker sequence lobes, with high energy permanence in proximal zones of the deposit versus high cyclicity in distal or intermediate zones, 2) Units of greater textural maturity and granulometric selection, where porosity occlusion caused by cement precipitation is not significant, and 3) The flow condition enhanced by the presence of microfracturing.