Optimization Design Of Oil Well Fracturing Scheme In Block X Of Daqing Oilfield

With the deepening of oilfield development,after long-term water drive development,the remaining oil in the formation of conventional old oilfields gradually decreases.Fracturing can change the original water drive flow channel and increase the oil production of oil wells.After long-term water drive development,the oil production of oil wells in block X of Daqing Oilfield is gradually reduced,and it is necessary to increase production by fracturing.However,block X has three target reservoirs,and the two layers are close to each other.Therefore,layered fracturing cannot be realized by using conventional segmented fracturing technology.Therefore,flow limiting method needs to be used to control the initiation of reservoir fractures and make each layer can be used better.In this paper,the fracturing scheme optimization design of block X in Daqing Oilfield is carried out based on the principles of safety,environmental protection,high efficiency and economy.In order to keep the proppant deep in the formation,a certain concentration of liquid CO₂ is added to the sand carrying liquid system to strengthen the flowback of the fracturing fluid.The concentration of carbon dioxide is simulated and optimized by using stimplan fracturing software,and the final concentration is determined to be 10%.Relying on the gas energy to carry the fracturing fluid system and reduce the ability of fracturing fluid to carry proppant can effectively ensure the fracture size and fracture conductivity,and optimize the basic reservoir parameters such as fracture half length and conductivity,as well as the construction parameters such as wellhead construction pressure.The results show that:(1)The formation brittleness index is high,the young's modulus is high,the in-situ stress difference coefficient is small,the bedding fracture is developed,and the reservoir compressibility is good.The change between vertical principal stress and horizontal principal stress at the target well section is predicted.(2)The optimal fracturing fluid formula is 0.3%polymer+0.1%bactericide ads-1+0.5%drainage aid adb-1+0.5%foaming agent adfp-1+0.5%clay stabilizer adn-1+0.12%Na2CO3+0.3%temperature stabilizer adpt-2;The crosslinking agent is organic boron crosslinking agent.(3)When the amount of carbon dioxide in the fracturing fluid system is less than 10%,the proppant loss rate after flowback is low and the fracture conductivity is relatively high.When the pumping speed is less than 2.8m³/min,the fracturing fluid filtration is large,the proppant loss during flowback is large,the effective fracture width is narrow and the conductivity is reduced.When the pumping speed is greater than 3.8m³/min,the fracture height is too high under unrestricted conditions,the half length of effective fracture after fracturing is less than 10m,so the construction displacement is determined to be 2.8m³/min-3.8m³/min.(4)The overall effect is poor,so it is necessary to carry out separate optimization design for the control technology of fracture height,and the overall fracturing sequence is:press the third section first,and then the first and second fracturing sections.There is no interference between the 19th and 20th sublayer,and the fracturing effect is good.For the 19th sublayer,the fracture half length is about 48m,and the fracture half length of the 20th sublayer is about55m,which has achieved the expected fracturing effect.Taking block X of Daqing Oilfield as an example,under the condition of considering different stimulation measures,this paper further optimizes the fracturing parameters,provides development potential for the follow-up development of other measures,and provides accurate production data for the combination of various measures in the later stage of old oilfield development.