袖套式射孔压裂复合技术在濮城油田的应用

濮城油田沙三段储层致密 ,普通射孔枪射孔后必须实施二次压裂技术 ,才能改善提高油层导油能力 ,成本高 ;而袖套式射孔压裂复合技术可在射孔的同时对地层进行压裂 ,且压裂效果好 ,造缝能力强 ,裂缝延伸长 ,成本低 ,濮城油田应用实施后 ,经济效益显著     

对水力压裂裂缝延伸方向平行于断层的认识

油田开发研究与实践认为，水力压裂裂缝延伸方向总是平行于地层最大水平主应力方向或垂直于断层走向，濮城油田沙三段油藏2001年压裂裂缝监测显示，一半以上压裂井的裂缝延伸方向平行或近似平行于主断层或次级断层，重新认识研究后认为这种情况确实存在，深入研究其内在原因并提出准确预测压裂裂缝延伸方向的解决办法，对油田开发并网的部署和压裂措施的实施具有重要指导意义。     

微震监测技术在濮城油田沙三上5-10油藏的研究与应用

濮城油田沙三上 5 - 1 0油藏是一套非均质性严重的低渗油藏 ,在开发过程中进行人工压裂是该储层进行油藏改造的主要方法之一。微震监测技术能有效检测出储层的裂缝方向、长度和裂缝高度 ,对压裂措施效果分析 ,避免处在注水井水线方向的油井暴行水淹、确定注入水推进方向及剩余油分布规律具有较强的理论依据 ,是油藏压裂改造中不可缺少的一项监测资料。     

浅谈井况治理与预防

随着濮城油田进入老油田开发阶段,地下认识、措施挖潜、油藏经营等各项工作都为我们提出了更高的要求。濮城油田地质构造复杂,有盐层发育、井深、高温、高盐、高压及高矿化度等特点。在油田开发过程中,压裂、补孔、高压注水等油田增产措施的实施,客观上加剧了油水井套管损坏,形成了大量的复杂事故井。     

葡萄花油田水平缝重复压裂改造技术

针对大庆油田长垣人工裂缝为水平缝的重复压裂井,以葡萄花油田为研究对象,初步界定了重复压裂选井选层工艺方法;应用试井分析和流动指数方法判断重复压裂时机;经过研究找出了重复压裂井裂缝失效的主要原因。根据裂缝失效的原因,确定了增大施工规模、酸洗裂缝以及多裂缝、开新缝压裂等项改造措施。结合理论研究在葡萄花油田现场试验,取得较好效果。     

濮城油田沙三中9砂组剩余油挖潜研究

濮城油田沙三中6-10油藏于1980年发现,1983年投入试采.由于沙三中油藏埋藏深、油层物性差、油井自然产能低,长期以来作为难采储量未投入开发.近年来在深化油藏地质研究的基础上,对濮城油田沙三中9砂组剩余油分布进行了研究,结合油藏自身特性,确定了小井距压裂改造的治理方案,收到良好的效果.     

超低渗储层压裂裂缝形态研究

近几年来,随着我国油量需求的不断增加,各个油田相继得到开发,然而超低渗出层具有压力低以及渗透性低的特点,增加了油田在开发的过程中的难度,制约了我国油田勘探。鉴于此种现象,水力压裂能够实现超低渗储层的有效开发,研究压裂裂缝形态对油田的开采有着重要意义。本文首先阐述超低渗出层开发的难点、改造的新思路以及多裂缝的压裂技术,分析超低渗储层压裂的裂缝形态,以望对油田的勘探有一定的借鉴意义。     

七里村油田压裂裂缝研究

压裂是低渗透油田油层改造最有效的方法之一,本论文通过对七里村油田主力油层长6油层的岩石破裂后裂缝进行研究,详细描述人工裂缝的形态和延伸规律,从而明确该区人工裂缝类型与形态,并通过压裂后的裂缝检测得到对裂缝更加详细的认识。     

裂缝监测技术在水平井中的应用

水平井可在薄油层中增大井筒过油层范围,实现高速注采,提高产能。某油田区块投产水平井均采用水力压裂投产方式完井,而经济有效的水力压裂应尽可能地让裂缝在储层内延伸,防止裂缝穿透水层或低压渗透层。现场作业表明,水力压裂的效果往往不十分明显,有时由于穿透隔层导致失败,造成油层压力体系破坏,影响油田的整体开发效果。因此常常需要了解、研究裂缝扩展规律并采取有效措施控制裂缝的扩展形态,从油田实践看,由于受监测手段的限制,对裂缝扩展规律的认识还十分有限。该油田通过应用微地震裂缝监测技术、压裂前后密闭井温测试、大地电位等多种裂缝监测技术,进行裂缝扩展规律的认识和研究,并通过多种裂缝监测结果比较,对水平井压裂过程中产生的人工裂缝形态有了较为清楚的认识,且对区块内其它水平井压裂过程中的施工控制及压后的效果分析有十分重要的指导作用。     

微地震裂缝监测技术在油水井压裂和注水评价中的应用

微地震裂缝监测技术使用现代声发射技术中平面任意三角形阵列的源定位方法,结合计算机数据处理技术和相关的油田地质参数,可在屏幕上实时显示数千米深岩层人工裂缝的变化形态和方位状况,开创性地应用高新技术手段指导油田开采,达到了提高工作效率、增加原油产量的目的。文章以微地震裂缝监测技术对火烧山油田压裂井监测及彩南油田注水井组监测结果,评价了注水井组的水窜方向和压裂井裂缝的形态、方向及长度,对油田压裂效果评价和油田后期注采井网调整起到了重要的指导作用。     

Hertzian Fracture of Vitreous Carbon

Hertzian fracture produced by steel ball indenters on vitreous carbon is qualitatively similar to Hertzian fracture of soda-lime glass. The bulk material obeys Auerbach's law, i.e. the critical fracture load is proportional to the ball radius. However, a surface layer of material, which is denser than the bulk, is stronger and does not obey Auerbach's law. The fracture energy calculated from Auerbach's law and the theory of Frank and Lawn is more than an order of magnitude lower than that measured by conventional methods. Part of this discrepancy arises from the fact that the ring crack is 17% larger than the circle of contact. The fracture surface energy of vitreous carbon as determined by a somewhat empirical application of Auerbach's law is ∼3.5 J/m². The Hertzian fracture stress of vitreous carbon, like that of soda-lime glass, approaches the transverse rupture strength (TRS) when large indenters are used.     

Size Effect in Fracture of Ceramics and Its Use To Determine Fracture Energy and Effective Process Zone Length

The paper shows that a previously proposed size effect law can be used to identify nonlinear fracture properties solely from measured maximum loads of geometrically similar ceramic fracture specimens of sufficiently different sizes. This law represents a first-order global approximation of the deviations from linear elastic fracture mechanics, independent of the type of the toughening mechanism in the fracture process zone. It provides a simple and unambiguous way to determine the size- and shape-independent values of the fracture energy the effective length of the process zone, and the effective crack-tip opening displacement. It also yields the R curve, which is geometry (shape) dependent. The proximity of response to linear elastic fracture mechanics is characterized by a brittleness number, which is shape independent.     

Crack Propagation Law Affected by Natural Fracture and Water Jet Slot under Blast Loading

The natural fracture of rock has a strong effect on the law of explosion stress wave transmission and crack propagation during blasting. Based on the stress wave theory, the influential mechanism for both the law of transmission of the stress wave and of crack propagation due to natural fracture and water jet slot are analysed. Next, an experiment is conducted to understand the crack propagation law because of the effect of an explosion shock wave, and the evolution law of the blast stress wave and blast-induced crack propagation is simulated by ANSYS/LS-DYNA. The results indicate that the existence of the water jet slot not only promotes the generation of the main crack along its direction, but also promotes the generation of the secondary crack near the water jet slot because of the explosion shock wave. The direction of propagation of the secondary crack and the main crack are seriously affected by the natural fracture. In addition, if the distance between the blast hole and the natural fracture is too small, a smash area is formed; and with an increase in the distance between the blast hole and the natural fracture, the smash area becomes smaller, and the effect on the blast-induced crack becomes weaker.     

Entropy and melt fracture

The onset of a well-known flow instability commonly called “melt fracture” has remained one of the fundamental unsolved problems of polymer rheology. This work attempts to explain this phenomenon via a criterion based upon limitations to configurational entropy as dicated by the second law of thermodynamics. It is shown that the molecular orientation resulting from a sustained stress-deformation rate field may be sufficient to affect the entropy balance of the system to the point of violation of the second law. The flow field then spontaneously changes, producing the condition called melt fracture, in a manner such as to prevent the violation of this law. Other theories on the mechanism of melt fracture are discussed in the context of the above criterion.     

A model law for the notch sensitivity of brittle materials

In this paper a model law for the notch sensitivity of brittle materials, for instance hardened cement paste, mortar or concrete is presented. This model law shows that notch sensitivity is a necessary however not a sufficient condition for the applicability of linear elastic fracture mechanics. The model law indicates that notch sensitivity of a brittle material decreases with increasing fracture toughness, decreasing tensile strength and decreasing specimen size. The model law explains the increase of the net failure stress of notched specimens with increasing notch depth after passing through a minimum. Such behavior frequently has been observed in experiments on hardened cement paste, mortar and concrete specimens. Results of flexure tests on notched and unnotched hardened cement paste specimens and concretes of various sizes are in accord with the model law.     

Influence of Layer Thickness on Cohesive Properties of an Epoxy-Based Adhesive—An Experimental Study

Cohesive laws are determined for different layer thicknesses of an engineering adhesive. The shape of the cohesive law depends on the adhesive layer thickness. Of the two parameters of the cohesive law—the fracture energy and the strength—the fracture energy is more sensitive to thickness variation than the strength. The fracture energy in peel mode (Mode I) increases monotonically as the thickness is increased from 0.1 to about 1.0 mm. At an adhesive thickness of 1.5 mm, the fracture energy is slightly lower than for a 1.0 mm adhesive thickness, indicating a maximum between 1.0 and 1.5 mm. In shear mode (Mode II), the thickness dependence is not as strong, but an increasing trend in fracture energy with increasing adhesive thickness is evident. A slight decrease in strength with increasing adhesive thickness is found in both loading modes.     

Size-Effect on the Fracture Toughness and the R-Curve of Carbon Materials

A theoretical extension of the Bažant size-effect law to crack propagation problems is made in order to analyze the R -curve-related microfracture mechanisms of brittle materials. The specimen's size-effect on the fracture toughness and crack growth resistance curve ( R -curve) is formulated in a generalized fashion without assuming the similitude restriction of test specimen geometry, being more convenient for the study of R -curve behavior. Using the size-effect law proposed in this work, the dimensions of the crack-tip process zone as well as the crack-face bridging region are estimated in the fracture mechanics analysis of carbon materials (a polycrystalline graphite and a carbon-matrix/ carbon-fiber composite). Microstructural observations confirm these fracture mechanics estimates.     

浅层砂岩垂直井分段压裂起裂压力研究

浅层砂岩垂直井分段压裂,初次裂缝压裂的产生会对后续缝的起裂压力产生影响.在综合考虑了原始井筒周围地应力场的基础上,结合叠加原理和弹性力学理论,建立了浅层砂岩诱导应力场中井筒周围应力场应力分布模型和起裂压力的计算模型.研究结果表明:诱导应力场的分布受裂缝缝长、裂缝间距和原始地应力场的影响.在初次裂缝缝长一定的前提下,裂缝间距越小对诱导应力的影响越大.在裂缝间距一定的前提下,裂缝缝长越长对诱导应力场的影响越大.     

In-Plane Fracture Resistance of a Crossply Fibrous Monolith

The in-plane fracture resistance of a crossply Si₃N₄/BN fibrous monolith in the 0°/90° and ±45° orientations is examined through tests on notched flexure specimens. The measurements and observations demonstrate the importance of fiber pullout following fiber fracture. The mechanical response is modeled using a crack-bridging approach. Two complementary approaches to evaluating the bridging law are developed: one based on a micromechanical model of fiber pullout and the other based on the load versus crack mouth opening displacement response of the flexure specimens following fracture of all fibers. Both approaches indicate that the bridging law follows an exponential form, characterized by a bridging strength and an effective pullout length. An assessment of the bridging model is made through comparisons of simulations of the load–displacement response with those measured experimentally.     

Fatigue of Yttria-Stabilized Zirconia: II, Crack Propagation, Fatigue Striations, and Short-Crack Behavior

Fatigue crack propagation in 3Y-TZP was investigated using controlled surface flaws. A unique growth law strongly dependent on the maximum stress intensity factor and quadratically dependent on the amplitude of the range of stress intensity factor was established. This growth law was found to apply for both surface flaws and internal flaws and could be used to predict fatigue lifetime. The presence of residual stress altered the growth mechanics so that an inverse growth rate dependence on the applied stress, reminiscent of the so-called "short-crack behavior," was manifested. Fatigue striations resulting from alternate overload fracture and fatigue fracture during stress cycling were observed. The appearance of striations varied with the R ratio and was very sensitive to the loading condition and crack geometry.