石油钻探技术
石油鑽探技術
석유찬탐기술
PETROLEUM DRILLING TECHNIQUES
2015年
4期
83-90
,共8页
煤层气%割理%水力压裂%起裂压力%物理模型%数学模型
煤層氣%割理%水力壓裂%起裂壓力%物理模型%數學模型
매층기%할리%수력압렬%기렬압력%물리모형%수학모형
coal bed methane%cleat%hydraulic fracturing%fracture initiation pressure%physical model%mathematical model
煤岩内部存在大量割理、裂隙等结构弱面，水力压裂时裂缝起裂可能发生于煤岩本体或割理裂隙处，造成其裂缝起裂机理与常规砂岩储层有较大差别，需要建立新的适用于煤层气井的裂缝起裂压力计算模型。考虑煤岩割理系统交割网状分布特性以及割理的空间位置变化关系，基于岩石力学和断裂力学理论，推导了煤层裸眼井壁和射孔孔壁周围及割理壁面处的应力分布方程；基于张性和剪切起裂条件，建立了煤岩不同完井方式下的裂缝起裂压力计算模型。应用该模型对2口压裂井进行了计算，裸眼和射孔完井裂缝起裂压力计算值与实测值之间的误差分别为3.96％和4.72％，表明该模型的计算结果与实测结果吻合较好。研究结果表明，煤层压裂能够从割理处起裂，起裂压力与煤层割理倾角、割理壁面内摩擦系数以及煤层水平主应力差值等因素密切相关。
煤巖內部存在大量割理、裂隙等結構弱麵，水力壓裂時裂縫起裂可能髮生于煤巖本體或割理裂隙處，造成其裂縫起裂機理與常規砂巖儲層有較大差彆，需要建立新的適用于煤層氣井的裂縫起裂壓力計算模型。攷慮煤巖割理繫統交割網狀分佈特性以及割理的空間位置變化關繫，基于巖石力學和斷裂力學理論，推導瞭煤層裸眼井壁和射孔孔壁週圍及割理壁麵處的應力分佈方程；基于張性和剪切起裂條件，建立瞭煤巖不同完井方式下的裂縫起裂壓力計算模型。應用該模型對2口壓裂井進行瞭計算，裸眼和射孔完井裂縫起裂壓力計算值與實測值之間的誤差分彆為3.96％和4.72％，錶明該模型的計算結果與實測結果吻閤較好。研究結果錶明，煤層壓裂能夠從割理處起裂，起裂壓力與煤層割理傾角、割理壁麵內摩抆繫數以及煤層水平主應力差值等因素密切相關。
매암내부존재대량할리、렬극등결구약면，수력압렬시렬봉기렬가능발생우매암본체혹할리렬극처，조성기렬봉기렬궤리여상규사암저층유교대차별，수요건립신적괄용우매층기정적렬봉기렬압력계산모형。고필매암할리계통교할망상분포특성이급할리적공간위치변화관계，기우암석역학화단렬역학이론，추도료매층라안정벽화사공공벽주위급할리벽면처적응력분포방정；기우장성화전절기렬조건，건립료매암불동완정방식하적렬봉기렬압력계산모형。응용해모형대2구압렬정진행료계산，라안화사공완정렬봉기렬압력계산치여실측치지간적오차분별위3.96％화4.72％，표명해모형적계산결과여실측결과문합교호。연구결과표명，매층압렬능구종할리처기렬，기렬압력여매층할리경각、할리벽면내마찰계수이급매층수평주응력차치등인소밀절상관。
There are many cleats ,fractures and other structural weak planes in coal seams .Fractures may origin from coal body or cleat cracks during hydraulic fracturing .Consequently ,mechanisms related to fracture initiation may be significantly different from those observed in conventional reservoir forma-tions .In this regard ,a new calculation model of fracture initiation pressure suitable for gas wells in coal-bed methane formations should be established .Considering the delivery network distribution characteris-tics of the coal seam cleat system and change of cleats in their spatial positions ,the stress distribution a-round the perforated holes and cleats walls was determined based on the rock mechanics and fracture me-chanics theory .According to conditions related to tensile and shear failures ,the calculation model for frac-ture initiation pressure of coal was established under different well completion methods .The calculation model was used for two fractured wells and the fracture initiation pressure difference between the calculat-ed value and the measured value in the conditions of open hole completion and perforated completion were 3 .96% and 4 .72% ,respectively .It could be seen that the calculated results coincided well with measured values .The results showed that a seam fracture could be generated from cleats ,and the fracture initiation pressures were closely related to coal bed cleat angle ,coefficient of internal friction of cleat walls ,coal bed horizontal principle stress differences and other factors .
