Abstract
There are a lot of tight gas formations with high temperature and high pressure in the south of Songliao basin in northeast China. However, it is very difficult to conduct successful fracturing treatment jobs as results of deep wells (more than 4200 m), high temperature (more than 150°C) and high pressure (more than 60 MPa), etc. Therefore, a systematic studies have been performed to overcome above mentioned difficulties, and the highlights are: 1) Fine formation evaluations prior to fracturing treatment; 2) A new finely processed Guar is developed, and the concentration is only 0.45% for the temperature of 150°C, and residue content 125 mg/l correspondingly, both are much less than those of commonly used Guar system; 3) Smaller sized proppant with high strength is optimized, sometimes, more than two proppant types or sizes is also chosen comprehensively; 4) Fuzzy undetermined analysis of economic benefit is performed to optimize propped fracture length and conductivity, in which the Monte-Carlo method is utilized; 5) Many fracturing treatment parameters are changed and combined optimizedly such as proppant's type and size, fracturing fluid's type, cross linked ratio, concentration of based fluid, concentration of gel breaking agent, and pumping rate as well, which makes it not only to ensure the successful treatment but also to minimize fracture damage so as to maximize fracturing treatment potential; 6) Spiral mode of proppant pumping schedule is put forward in order to prevent earlier screen-out; 7) A new forced fracture closure technique is utilized to improve propped profile in the case of multiple payzones. Above low damage and massive fracturing technique was put in to filed applications in 6 gas wells, all treatments were completely successful with the maximal proppant weight being as high as 165,000 kg, while in the past, there were many treatment failures. And the highest post-fracturing rate 70,000 m3/d, which is satisfied as expected. So, it has a great significance not only in improving fracturing treatment effect in above mentioned gas formations but also in perfecting low damage and massive hydraulic fracturing technique as well.
