發(fā)布時間：2018-03-15 07:41

  本文選題：波動壓力　切入點：巖屑床　出處：《西南石油大學》2017年碩士論文　論文類型：學位論文

【摘要】：對于窄安全密度窗口地層,起下鉆過程中的井內(nèi)壓力瞬時波動,可能會導致井壁失穩(wěn)發(fā)生井漏、井噴,所以波動壓力的準確預測對于井控、控壓鉆井和鉆井參數(shù)優(yōu)化至關(guān)重要。在水平井和定向井的鉆井過程中,極易在大斜度的偏心環(huán)空中形成巖屑床,巖屑床形成后不僅會增大摩阻扭矩,還會對環(huán)空流動產(chǎn)生較大影響。為了實現(xiàn)存在巖屑床時的偏心環(huán)空波動壓力的準確便捷預測,本文首先以流體力學理論為基礎(chǔ),建立同心環(huán)空屈服冪律流體閉口管波動壓力擬合模型、偏心環(huán)空屈服冪律流體閉口管穩(wěn)態(tài)波動壓力數(shù)值模型和偏心環(huán)空屈服冪律流體波動壓力比率擬合模型;其次基于Fluent軟件,開展考慮巖屑床影響的同心環(huán)空和偏心環(huán)空波動壓力仿真實驗。最后在通過引入當量水力直徑的基礎(chǔ)上,利用CFD仿真結(jié)果分別建立考慮巖屑床影響的同心環(huán)空和偏心環(huán)空波動壓力簡化模型。取得的主要研究成果有:(1)波動壓力隨起下鉆速度、屈服值和稠度系數(shù)的變化呈(擬)線性變化,隨流性指數(shù)、環(huán)空內(nèi)外徑比率和偏心率的變化呈指數(shù)性變化;基于同心環(huán)空和偏心環(huán)空屈服冪律流體波動壓力數(shù)值模型結(jié)果,建立的屈服冪律流體同心環(huán)空波動壓力擬合模型和偏心環(huán)空波動壓力比率擬合模型,誤差分別為0～+10%和±5%;擬合模型預測結(jié)果比較接近于數(shù)值精確模型預測結(jié)果,即擬合模型具有比較高的計算精度;(2)沿徑向方向的"中間疏,兩頭密"的網(wǎng)格模型適用于考慮巖屑床影響的波動壓力預測;同心和偏心環(huán)空波動壓力隨著巖屑床的厚度增加,呈先增大后減小的趨勢;當巖屑床厚度相同時,波動壓力隨著起下鉆速度、屈服值、稠度系數(shù)、流性指數(shù)的增大而增大;(3)同心和偏心環(huán)空平均巖屑床壁面切應力隨著起下鉆度、屈服值、稠度系數(shù)、流性指數(shù)的增大而增大;同心環(huán)空中,當巖屑床厚度小于環(huán)空間隙時,巖屑床最易全部清除,當巖屑床厚度剛接觸內(nèi)管壁附近時,巖屑床最難完全清除,偏心環(huán)空中,當巖屑床厚度小于環(huán)空間隙時,巖屑床最難全部清除,當巖屑床厚度剛接觸內(nèi)管壁附近時,巖屑床最易完全清除;(4)通過引入有效水力直徑的方法能夠?qū)崿F(xiàn)考慮巖屑床影響的同心環(huán)空和偏心環(huán)空波動壓力的簡單準確預測,與CFD仿真結(jié)果相比,修正后當量水力直徑擬合模型的預測精度能得到大幅提高,同心環(huán)空誤差范圍為-5%～10%左右,偏心環(huán)空誤差范圍為±11%左右。
[Abstract]:For the formation with narrow safe density window, the instantaneous fluctuation of the pressure in the well during the process of hoisting and drilling may lead to the leakage and blowout of the wellbore instability, so the accurate prediction of the fluctuating pressure is controlled by the well. In the drilling process of horizontal well and directional well, cuttings bed is easily formed in the eccentric annulus with high inclination, and the friction torque is not only increased after the formation of cuttings bed. In order to realize accurate and convenient prediction of eccentricity annulus wave pressure in the presence of cuttings bed, this paper is based on the theory of hydrodynamics. The numerical model of steady state wave pressure of yield power law fluid in eccentric annulus and the fitting model of wave pressure ratio of yield power law fluid in concentric annulus are established. Secondly, based on Fluent software, the numerical model of steady wave pressure of yield power law fluid in eccentricity annulus and the model of wave pressure ratio of yield power law fluid in eccentric annulus are established. The simulation experiment of wave pressure in concentric annulus and eccentric annulus considering the influence of cuttings bed is carried out. Finally, on the basis of introducing equivalent hydraulic diameter, Based on the CFD simulation results, the simplified models of wave pressure in concentric annulus and eccentric annulus considering the influence of cuttings bed are established, respectively. The change of yield value and consistency coefficient is (quasi-) linear and exponentially varying with the flow index, the ratio of inner diameter and outer diameter of annulus and eccentricity, and based on the numerical model of the pressure of yield power law fluid in concentric annulus and eccentric annulus. The fitting model of the concentric annulus pressure of yield power law fluid and the ratio of eccentric annulus wave pressure with the error of 0 ~ 10% and 鹵5 respectively, the predicted results of the fitting model are close to those of the numerical accurate model. That is to say, the fitting model has a high calculation accuracy, and the meshing model with "middle thinning and dense at both ends" along the radial direction is suitable for predicting the fluctuating pressure considering the influence of the cuttings bed, and the concentric and eccentric annulus fluctuating pressures increase with the thickness of the cuttings bed. When the thickness of cuttings bed is the same, the fluctuating pressure increases with the increase of drilling speed, yield value, consistency coefficient and flow index. In concentric annulus, when the thickness of the bed is less than the gap of annulus, the bed of cuttings is most easily cleared, and when the thickness of the bed of cuttings is in contact with the inner pipe wall, it is the most difficult for the bed to be completely removed. In eccentric annulus, when the thickness of cuttings bed is smaller than the annular gap, the cuttings bed is the most difficult to be completely removed, and when the thickness of the cuttings bed is in contact with the inner pipe wall, By introducing the effective hydraulic diameter method, the simple and accurate prediction of wave pressure in concentric annulus and eccentric annulus considering the influence of cuttings bed can be realized, and compared with the CFD simulation results. The prediction accuracy of the modified equivalent hydraulic diameter fitting model can be greatly improved. The error range of concentric annulus is about -5% and that of eccentric annulus is about 鹵11%.
【學位授予單位】：西南石油大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TE21

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