Significant Production Improvement of UltraLow Permeability Granitic Reservoirs to Develop Heavy Black Oil, Utilizing Channel Fracturing Technique

摘要

The development of low quality reservoirs such as; low permeability, marginal assets, and unconventional resources has a several cost challenges pushing the industry toward maximizing the potentiality and optimizing the strategies of such high risk plays. Petrobel has a discovered one of such challenged asset and successfully conducted a comprehensive study to set the best development strategy to unleash this potential. SIDRI Area is a relatively new settlement with a reasonable hydrocarbon potential according to petrophysical analysis. The target formation of SIDRI wells is a sedimentary rock with granitic facies that consist of a series of tight conglomerates over an oil/water column of more than 900m. The pore system of this rigid and stiff formation consists of a micro natural fractures network with secondary cemented porosity. The production is mainly governed these tiny natural fractures that have a permeability as low as 0.1-0.5 md. Despite this tightness these series are separated by nonporous sections that occasionally exhibit as barrier and may introduce layering or subdivision of pay, however in sometimes permit a vertical communication between productive sections. Performed Cuttings analysis such as XRD, thin-sections showed a variety of minerals composition representing different lithology which in turn complicates the characterization of such reservoir. On top of the unique mineralogy, the executions of fracturing treatment of SIDRI wells include multiple other challenges. The higher reservoir temperature and the formation depth cause a great constraint in terms of pumping rate and pressure. Besides, the non-availability of pumping equipment of high Horsepower restricts the pump rates and also limits the utilization of slick water frac. Even the nature and the quality of crude oil is quite challenged since it is a heavy black oil type and its composition contains high number of asphaltenic compounds accordingly the opportunity of creating sludge with treatment fluids is highly likely. The oil water viscosity ratio at reservoir condition represents a weighted obstacle for oil recovery that should be overcome. The basic concept of applying hydraulic fracturing for these kinds of reservoirs is very simple, however the execution to get much more production improvement is quite difficult. Particularly the main idea here is to conduct a cost effective fracturing treatment with economical wisdom principle that can lead to achieve a greater oil recovery with best profitable model. This paper presents the details of formation characterization and reservoir quality assessment, as well as a detailed discussion about wettability alteration and how adversely complicates the process of determining initial saturation. The implemented application including designing, experimental works, and execution of the channel fracture treatment job will be reviewed. The work sequence of this project that led to commercialize such asset will be addressed too.