CAJ | 학술논문

大庆长垣外围低渗透油藏水驱开发受注水动态裂缝影响，水驱开发效果差。为改善水驱效果，需首先明确注水动态裂缝开启规律，进而才能提出开发调整对策。综合利用地质力学、油藏工程及数值模拟等方法，建立了注水动态裂缝开启压力计算方法，揭示了其开启机理和延伸规律，并针对裂缝开启不同情况，形成了相应的调整对策。研究表明：当注水压力超过储层现今最小水平主应力时，裂缝首先沿现今最大水平主应力方向开启；随着注水压力继续增加，裂缝沿与现今最大主应力方向夹角较小的注采井连线方向开启。根据裂缝开启压力计算方法，结合大庆外围A油藏条件，其裂缝开启的临界注水压力为9 MPa。油藏注水压力为12～14 MPa，当注水井排与现今最大水平主应力方向一致时，油藏沿现今最大水平主应力方向开启单方向裂缝，剩余油主要沿裂缝呈条带状分布；当注水井排与现今最大水平主应力方向呈一定夹角时，油藏开启多方向裂缝，剩余油被多方向裂缝切割呈零散分布。基于不同井网与裂缝匹配油藏剩余油分布模式，提出了“限压注水控制多方向注水动态裂缝开启、沿现今最大水平主应力方向裂缝线性注水、侧向基质驱替”的开发新理念，给出了注水压力界限与井网加密调整模式，现场应用效果显著。
대경장원외위저삼투유장수구개발수주수동태렬봉영향，수구개발효과차。위개선수구효과，수수선명학주수동태렬봉개계규률，진이재능제출개발조정대책。종합이용지질역학、유장공정급수치모의등방법，건립료주수동태렬봉개계압력계산방법，게시료기개계궤리화연신규률，병침대렬봉개계불동정황，형성료상응적조정대책。연구표명：당주수압력초과저층현금최소수평주응력시，렬봉수선연현금최대수평주응력방향개계；수착주수압력계속증가，렬봉연여현금최대주응력방향협각교소적주채정련선방향개계。근거렬봉개계압력계산방법，결합대경외위A유장조건，기렬봉개계적림계주수압력위9 MPa。유장주수압력위12～14 MPa，당주수정배여현금최대수평주응력방향일치시，유장연현금최대수평주응력방향개계단방향렬봉，잉여유주요연렬봉정조대상분포；당주수정배여현금최대수평주응력방향정일정협각시，유장개계다방향렬봉，잉여유피다방향렬봉절할정령산분포。기우불동정망여렬봉필배유장잉여유분포모식，제출료“한압주수공제다방향주수동태렬봉개계、연현금최대수평주응력방향렬봉선성주수、측향기질구체”적개발신이념，급출료주수압력계한여정망가밀조정모식，현장응용효과현저。
The performance of water flooding in low permeability reservoirs of Daqing oilfield is not satisfied due to the dynamic induced fractures.Understanding of the opening mechanisms of the dynamic induced fractures and optimization of development adjustment schemes are critical to improving water flooding recovery.Geomechanics, reservoir engineering and numerical simulation methods were utilized to establish a new method to calculate the fracture opening pressure and reveal propagation mechanism.Corresponding adjustment measures are proposed for different fracture opening scenarios. Results indicate that when injection pressure exceeds the current minimum horizontal principle stress, dynamic fractures will open first in the direction of the maximum horizontal principle stress.Then, they may open in the direction of line connecting injector and producer that has the smallest included angle with current maximum principle stress along with the rising injection pressure.Based on calculation methods of fracture opening pressure and in combination with the con-ditions of A reservoir in the periphery of Daqing oilfield, a critical injection pressure of 9 MPa is determined for fracture opening.Actually the injection pressure of A oilfield is up to 12~14 MPa.When the line of injection wells is in parallel with the current maximum horizontal principle stress, fractures only open in the direction of the maximum horizontal prin-ciple stress, and remaining oil are distributed along the fractures on both sides.Otherwise, fractures open in multiple di-rections, and the remaining oil distribute irregularly.Based on the remaining oil distribution under different well patterns, a new concept is proposed that‘controlling the opening of multi-directional dynamic fractures through limiting injection pressure and line flooding along the dynamic fracture in parallel with the maximum horizontal principle stress and lateral matrix displacement’ .Water injection pressure limits and well pattern adjustment strategies are proposed under the gui-dance of this concept, and their field application is very successfully.