This paper deals with oil well cementing flash setting problem definition, interpretation and localization via PABM (phenomenon analysis-based method) and Swiss cheese model investigation. Cementing is the most critical job throughout the well realization process; it presents the face of the well during production or abandonment. Within cement job some, problems come out and could lead to lose the well objectives, and it can be classified as cementing program’s awkward or operational hitches. This work is oriented toward operational stage, even if cement program and preparation seem in the rules of the art, the execution stage can interrupt the smooth running of cement job. Flash setting is one of the most critical problems that could be occurred, and it can be recognized by the prior increases in pressure to reach unpumpable stage. Identifying flash setting phenomenon and distinguishing them from other operational comportment stay hard task and present the heart of this work. Consequences could be varied from simple cement left inside casing to total free pipe of the annulus. PABM together with cheese model is proposed to be used for deep analysis of flash setting problems and points out the real causes, if they exist, rather than flash setting. The method proposed includes five steps, description of the operation, phenomenon, assumptions, cheese model and conclusion. The three first steps construct operation scrutiny, and the fourth step represents PABM. In this latter method, assumptions will pass through a selective process made from operation facts, and only the adequate assumption reaches the last layer of the model. Practical cases have been detailed to point out the merit of this method and distinguishing flash setting from other related cement problems.
Heavy slurry pumping is facing enormous problems concerning pressure generation and casing limitations. Pumping high-density cement throughout narrow column, throttled at their extremity by the float equipment will generate more pressure, and could push casing to their limits of utilization. There are numbers of phenomena that could lead to casing length change as: piston, ballooning, temperature, tension and buckling. This work is oriented to study buckling effect on total casing length change. Generally, in conventional wells cementing, down hole conditions are referred to geological formation fracture pressure limit, which is lower than buckling limit. Heavy slurry displacement could make an exception, where buckling could appears at pressure inferior to geological fracture limit. While pumping heavy cement down, pressure inside casing increases progressively, pushing casing to extend, consequently risk of closing the narrow space out between casing and open hole total depth may appears. At this moment, buckling begins; pressure rise intensely to reach geological fracture limits and causes down hole loses. After passing the critical high pressure situation, casing will come back to their initial form. In order to overcome this situation, maximum allowable pressure during displacement together with problem indicators is proposed, to prevent and early detect the problem. Experimental and simulation results confirm the usability of assumption proposed.
This paper deals with a simulation of different power methods to detect and diagnose induction generator faults. Instantaneous partial and total power, active and reactive power, complex apparent power and transformed power from mechanic to electric nature are revisited, simulated and discussed in this paper for induction generator rotor broken bars and stator short cuts faults detection and diagnosis. Fast Fourier transform (FFT) and PQ transform algorithms are used as comparison tools. Simulation results show that, on one hand, active, reactive and complex apparent power can only be used to detect evolution of rotor faults. On the other hand, partial, total and power transferred from mechanical to electrical nature are able to detect induction generator faults evolution with the advantage of eliminating electrical distortions and influence of low quality of supplying voltage. Furthermore, the implementation of the PQ transformation offers the possibility to isolate load influence from rotor faults and stator ones.
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