Development of Systematic Hydraulic Fracturing Technology for a Naturally FracturedReservoir

摘要

Reservoir N is a typical low-permeability buried-hillrnfractured reservoir with oil-bearing area of 3.6Km 2 , OOIP ofrn973 ×10 4 t and buried depth of -1700 ～-2500m.Its oilrnbearing interval is longer, between 125 ～410m.Itsrnaverage porosity is 5.1% and average permeability is 23.6 ×rn10 -3 μm 2 . Due to the insufficient natural energy, its pressurerncoefficient is 0.98. As the economic yield can't be achieved byrnconventional technologies, the reservoir must be fracturedrnintegrally. Following technologies have been applied in thernfield. Based on early and proper water injection,rnsupplementing formation energy and maintaining formationrnpressure, fracturing and waterflooding are combinedrnreasonably to improve waterflooding sweep efficiency andrnavoid watering out and water channeling at the same time; thernconcept of optimizing fracturing design for high sand content,rnlarge discharge capacity, medium and low proppantrnconcentration and medium and long fractures is established sornthat artificial fractures can be communicated with naturalrnfractures and a complete interconnected system can be formedrnby pores, artificial and natural fractures in the reservoir; withrnthe method of perforating short intervals, avoiding perforatingrnlong intervals and staged fracturing, the whole oil-bearingrninterval is divided into 2 to 4 fracturing units which arernfractured from bottom to up till all the interval are fractured;rnsilt is used as the fracturing fluid loss additive to reducernexcessive fracturing fluid loss and used for propping fracturesrnand connecting major fractures and natural microfractures.rnReservoir N has been fractured for 96 times by this methodrnwith cumulative oil production of 98.3 ×10 4 t. Fieldrnapplications indicate that the method of integral fracturingrndevelopment is also suitable for the low-permeability fracturedrnsandstone reservoirs which are similar to Reservoir N and good development effects have been got.