Integrated Fracture Performance and Formation Damage Assessment to Enhance Well Production in the Hassi Messaoud Field, Algeria: Case Study

摘要

This paper discusses the causes of performance failure of a well in the Hassi Messaoud field in Algeria that was fracture stimulated but did not achieve the expected production increase, and it discusses alternative methods to increase well production by integrating geology and petrophysics with production and well- test data. The well was perforated in sand B and in the upper section of sand C. It was initially tested at 5.07 m3/h (765 B/D), but within three months, production declined to 1.99 m3/h (300 B/D). Early studies suggested that the rapid decline was probably caused by near-wellbore formation damage during drilling. A fracturing program was designed to help remove well damage and restore flow capacity; however, negligible production increase was observed following the hydraulic fracturing. Initially, damage on the fracture face and uncleaned fracturing fluid were the suspected causes of the ineffective fracture stimulation. A new pressure-buildup test was performed to assess the effectiveness of the fracture stimulation, and detailed analyses indicated that the small reservoir size might have been the cause of the rapid pressure decline. The fracturing design was based on pressure data from the initial drillstem test (DST) at 388.9 kg/cm2 (5,531 psi). A post-fracture pressure-buildup test revealed that reservoir pressure had declined to 233.2 kg/cm2 (3,317 psi) after only producing 6901 m3 (43,406 bbl). The pressure-buildup analysis detected a fourth boundary that was not mapped during the original three-dimensional (3D) seismic survey. This fault reduced the well drainage area by a factor of four and was the cause of the rapid pressure decline during production. A recent seismic survey refined the geological map of the entire reservoir and confirmed the presence of this fault. Petrophysical analysis of sand C showed higher-quality rock than sand B; however, the resistivity decreased with increasing sand C depth, suggesting the presence of water. Lithology analysis confirmed that the decrease in resistivity was resulted from higher clay content and clay-bound water. Offset wells also confirmed that the oil-water contact (OWC) was approximately 70 m (229.7 ft) below the bottom of this well. Well productivity could have been significantly higher if the entire sand B pay was initially completed. To compensate for low-formation pressure, a gas-lift optimization procedure was performed to lift the fluid to surface with an initial production of 2.14 m3/h (323 STB/D). After two years, the reservoir pressure in this bounded section declined to 169 kg/cm2 (2,404 psi). This paper discusses an integrated approach to increase oil production from a well penetrating a geologically challenging environment. Integration of geology, petrophysics, seismic, production modeling, and gas lift with proper data acquisition helped prevent abandonment of this well, leaving behind potential reserves. This paper also discusses a case study in which a false-formation damage diagnosis could have led to reservoir mismanagement.