Case Study: Mixing Proppant Sizes To Control Pressure Dependent Leak-Off (PDL)

Abstract

fax 01-972-952-9435. AbstractOne of the main factors affecting fracture treatment completion in the Cardium formation in North West Central Alberta is PDL. PDL is determined from minifrac analysis completed prior to the main treatment. PDL can be treated and controlled with a combination of increased fluid rates, additional 50/140 proppant (100 mesh) in the pad and increased gel loadings. Yet in certain areas even these precautions will not achieve successful placement of job design or effective fracture properties.Common practice is to design for 80 to 100 Tonnes of ceramic proppant into each of these reservoirs, with an additional 5 to 7 Tonnes of 50/140 proppant in the pad to control PDL. In most areas this works effectively for controlling the competing fracture leak-off during the treatment. In the Northwestern Alberta Cardium area this approach has not been as successful and has caused concern about total proppant placement.An alternative approach for controlling fluid leak-off during the treatment has been to mix in a small amount (usually 5% by weight) of 50/140 proppant with the ceramic proppant in the early stages of the treatments to control the fluid leak-off in these areas. Treatment design engineers recognize the fracture conductivity issues caused by mixing different mesh sizes. However, utilizing this approach has resulted in full job completion and this paper will discuss the specific treatment designs required to drastically limit fracture treatment screenouts.