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Hamid Hashemalhosseini,Alireza Baghbanan
حميد هاشم الحسيني (استاد راهنما) عليرضا باغبانان (استاد راهنما)
Peyman Norouzi
پيمان نوروزي


دانشکده معدن
Doctor of Philosophy (PhD)


An Experimental Study of Oil Well Perforation under Earth’s In-situ Stress
Perforation is creating a hole in the casing and the cement sheath around it and hydrocarbon-containing layer to form a hydraulic connection between the oil reservoir and inside the well. So far, various methods have been proposed to perforation of wells that the shaped charges have been widely used. Different factors influence perforation performance and Depth of Penetration (DoP). These factors are generally divided into two types of controllable and uncontrollable factors. The variations of flow properties have been investigated in the previous researches. As we know, there is not a comprehensive research around the effect of perforation on the rock properties in the wellbore situation. The purpose of this study was to investigate the effect of in-situ stresses and shot density on DoP and created fracture patterns in concrete and limestone samples with surface and polyaxial/triaxial stress loading conditions. To achieve this aim, we designed and developed a polyaxial perforation test machine. Laboratory tests were performed on concrete and limestone blocks and cores under surface and downhole conditions. Taguchi’s orthogonal scheme and statistical analysis were used to optimize the number of tests and analysis of the results, respectively. Core samples and blocky targets were perforated in the surface and downhole (in the presence of true triaxial loading) conditions, respectively. The failure pattern and the variations of the ultrasonic P-wave velocity of the concrete and limestone targets were measured before and after the perforation job. The results show that increased stresses reduce DoP by up to 60%. Analysis of variance of DoP showed that the contribution of stress in direction of perforation (?z) is not so significant (12%) compared with the other off plane stress components (?x, ?y) which are about 49% and 39%, respectively. By increasing the shot densities of 4 spf to 6 spf, the measured DoP of the second charge was greater than that of the first charge.The failure pattern of the targets is more controlled by the loading conditions. Under surface conditions, the pattern of perforation fractures in the concrete and limestone cores was radial and regular. The tension cracks created in the perforated limestone and concrete under triaxial stress conditions followed the same part as under surface conditions (radial cracks), while the fracture patterns in the true triaxial loading conditions were oriented in the direction of the maximum horizontal stresses. The measured p-wave velocity showed that VP increases along the perforation hole from the beginning of the hole toward the block boundaries. It was found the loading conditions control the VP values along the shooting axis. In anisotropic loading mode, the velocity of P-waves in direction of the maximum stress was greater than minimum horizontal stress. In the isotropic loading condition, VP values were same along the direction perpendicular to the firing axis
اين مطالعه با هدفبررسي تاثير تنش هاي برجا و فاصله داري گلوله ها بر روي عمق نفوذ، الگوي شکست هدف،تغييرات خواص صوتي هدف و ارائه يک الگوي مشبک کاري مناسب انجام شد. آزمون هايآزمايشگاهي بر روي هدف هاي بلوکي و مغزه هايي از جنس سنگ آهک و بتن API RP-43در شرايط سطحي، در حضور تنش سه محوره معمولي و واقعيانجام گرفتند. نتايج نشان مي دهد که افزايش تنش هاي برجا باعث کاهش عمق نفوذ مي گردد.اين در حالي است که نقش تنش هاي عمود بر محور شليک گلوله از تنش هم راستا با محورشليک بارزتر است. با کاهش فاصله بين گلوله ها از 4SPF به 6SPFعمق نفوذ گلوله دوم افزايش مي يابد. نوع بارگذاري بر روي شکستگي هاي ايجاد شده دراطراف سوراخ مشبک کاري تاثير گذار است. بر اثر اعمالتنش سه محوره واقعي بسته به نسبت تنش افقي بيشينه به کمينه ترک هاي کششي در امتداد و يا با زاويه حداکثر 30درجه نسبت به تنش افقي بيشينه منتشر شده و در صورت اعمال تنش سه محوره معمولي ترک هايکششي در اطراف سوراخ مشبک کاري و در جهات مختلف با زاويه حدود 30 درجه نسبت بهيکديگر منتشر مي گردند. اندازه گيري زمان عبور پالس طولي اولتراسونيک نشان داد کهسرعت موج طولي) (V P از ابتدا تا انتهاي سوراخ مشبککاري و همچنين با افزايش فاصله عرضي نسبت به سوراخ مشبک کاري افزايش مي يابد. برايحالت بارگذاري سه محوره واقعي و معمولي روند تغييرات V P در امتداد سوراخ مشبک کاري بايکديگر متفاوت است. در حالت بارگذاري سه محوره واقعي مقادير V P نسبت به فاصله از مرکز سوراخ مشبک کاري در صفحهعمود بر تنش افقي بيشينه بيشتر از صفحه عمود بر تنش افقي کمينه است.

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