Integrated Gordian Technology And Theory Research Of Fracturing And Flowing Back

Fracturing plays an important role in the exploratory development of oil-gas resources. At the moment almost every outer well of Daqing oil field are low permeability layer(permeability is lower than 50×10-3μm2), they have the feature that the thickness of individual layer is too small, and the number of the oil layer is large, there are usually two or more layers need to be fractured in one well. Available fracture technology is: after the first layer is fractured picking up the string and fracturing the second and third layer, then pulling out the frac-string and tripping in the testing and requiring production string. Using this method not only the work strength is large,the cycle time is long and the data of pressure testing is not continuously,but also in the process of picking up string the fracture fluid that blow out of the tubing can pollute the surface, this do no good to the environment, meanwhile we can't metering the flowback volume exactly. For this reason, according to the these difficulty, using the combinated method of theoretical analysis and field experiment, we designed a battery immovable string which can fracture 2 layers at the same time,cleaning up the well and requiring production and testing the well temperature. Following is the outcome of this resrarch.(1) Mechanics design Designing a suit of fracturing,cleaning up and requiring production,well temperature testing string using mechanics design low,furthermore designing and producing upper-packer,control switch,lower packer,pack off adapter,concentric large bore manometer barrel etc. more than 20 kinds of down hole equipment. Achieving technology that finishing two-layer fracturing,cleaning up and requiring production in one time but not move the string. It can decrease the work time,the damage of formation, alleviating the work strength,acnieving the aim of green working.(2) Theoretical analysis and application According to the unique feature of different formation optimizing the fracture fluid,addition agent and dispensation that have no affect on the oil-gas formation,ensured that the effectiveness of stimulation and increase production in the oil field is good. Using theory of rock breaking mechanics can obtain the theoretical model of the formation breakdown pressure. The formation breakdown pressure of Hailaer,Gulong and other block of Daqing oil field are calculated. Ensured that in the workover of immovable String two-layer Fracturing,Cleaning up and Requiring Production can fracture the formation and not cause communication between zones, at the same time down hole tools have enough overpressure resistant capability, so the work will be safe.Using the frac-string as our research target, adopting modern mechanics mrthod, considering the affect of string's buckle behavior as the main factor, establishing a general equation to describe the string's buckle behavior. Through the analysis of the equation, we know that the affection rule of string geometry,physical characteristics parameter and load etc. to the buckle behavior in the triaxial bended borehole. Using the method of modern mathematics analysis, we can compute string buckle equation, so we can obtain the result of three different condition(sine,coiling and bending,self-locking),interface buckled load and contacting normal pressure on the wellbore,analysising the affection of coulomb friction to the buckle behavior of string and axis force distribution in the hole. On the basis of recognizing wellbore string buckling behavior exactly, we can calculate and analysis the well bore string load,stress and aberration. When calculate practically, we considered the down hole equipment, such as packer etc. All these can offer theoretical reference to the reasonable option of producing parameter.Doing research about fluids rate forecast of low permeability formation vertical fracture well considering the affection of kick off pressure, when calculating, we must consider the affection of kick off pressure to the deliverability die-away law, describing the production changing curve following time under constant pressure and IPR curve under different time. Larger of the skin factor, lower the production of well early days, following time, the affection of skin effect will vanish. And the kick off pressure is larger,the producing pressure difference will be larger too. Kick off pressure have small affection to the early days production of fractured well, but on the later stage,the larger of kick off pressure, the lower of production; But with the increasing of kick off pressure, it can affect the production greatly, production drawdown is very marked. Achieving the accurate evaluation of low permeability and extra low permeability formation's deliverability.(3)Field experiment and application We carried on an experiment on the well simulator in the lab of layer mining evaluating petroleum engineering collage daqing oil field Ltd. The justifiability and sealing property of string system is verified;the setting and sealing property of upper and lower packer is verified; The reliability of down hole control switch and accuracy of pin shearing value is verified too. We also verified the reliability of fishing tool and the backwashing performance of upper packer using pressure increased experiment.On the exploration and development evaluation well of Daqing oilfield, this technology is applied on 31 wells, the success ratio is 100%.