Summary Conventional gravel pack completions often reduce the wells productivity by increasing the completion skin. This paper describes a methodology backed by a systematic technique to predict the necessary drawdown, frac length, and conductivity to prevent formation failure and remove the completion damage. This method enables the engineer to optimize the fracture dimensions while obtaining the necessary decrease in drawdown near wellbore that would cause the unpacked perforation to fail. This technique will greatly reduce the chance for formation failure and improve the well performance without the need to gravel pack. Introduction Gravel packing has been the standard practice for controlling sand production from producing wells. These treatments are considered successful if the well produces sand free with a minimum drawdown across the perforations. Considerable time, money and research has gone into developing techniques that improve the performance of gravel packed completions by minimizing the damage caused by the completion. Despite these efforts experience has shown that even the most sophisticated sand control technology affects well productivity because of near wellbore damage caused by the gravel pack procedure. Table 1 shows a comparison of skin and productivity index for over 70 wells that have been completed using various completion techniques. As can be seen even the best internal gravel packed wells experience high skins when compared to perforated non-gravel packed wells. It has also been known for a number of ears that applying relatively large volumes of grave at above fracture gradient pressures followed by a internal gravel pack have resulted in less damage and good productivity improvements. These operations, called "Sand Oil Squeezes", were effectively a combination of a gravel pack and a hydraulic fracturing treatment, and are now called "Frac and Pack's". This technology is now being advanced so that the fracturing part of a "Frac and Pack" is not only used to improve the well productivity but also as a sand remediation technique. The sand control is accomplished by reducing the pressure drop across the perforation. Previous investigators merely postulated probable physical mechanisms and field procedures, whereas this paper presents a theory that couples sand production prediction and fracturing. This technique is currently being used in the North Sea and, as described in this paper, in the Gulf Coast of the United States.

ESPAÑA RESUMEN SUMMARY INTRODUCCIÓNLa sal dc Friedel debe su nombre a que en 1897, Friedel (1) sintetizó el monocloroaluminato calcico hidratado, 3CaO AI2O3 CaCl2 AI2O3 lOH^. Esta sal de Friedel puede encontrase en una pasta de cemento, cuando dicha pasta está próxima auna fuente de cloruros. Las principales fuentes de cloruros son: las que provienen de echar NaCl y/o CaCl2 a las carreteras de hormigón para mantenerlas libres de hielo y nieve durante los meses de invierno en las regiones y/o países fríos; las que provienen de las fábricas de salazones y pescados; las que provienen de las aguas y ambiente marino en las zonas costeras y las que provienen del CaCl2 utilizado como acelerador del fraguado.La capacidad de fijación de los cloruros por el cemento depende de la naturaleza y composición de este último, de la cantidad de aluminato tricálcico presente en el clinker, de la sal clorada empleada, de la relación aguacemento, del tiempo de curado, etc. (2-13). Además, el ferrito-aluminato tetracálcico C^AF, también, es susceptible de formar la sal clorada análoga a la sal de Friedel, 3CaO Fe203 CaCl21OH2O (2,14). Sin embargo, y al igual que ocurre con los sulfatos, el C3A reacciona más rápidamente co n lo s cloruros que el C^AF, por lo que la mayoría de los complejos clorados inicialmentc formados en un OPC hidratado son sal de Friedel, de origen C3A.La sal de Friedel no sólo se puede formar en un cemento Portland ordinario sino que los iones cloruro se pueden enlazar también al aluminio de una escoria granulada de alto horno ( 15) y al aluminio de la alúmina reactiva, vitra o amorfa dc una puzolana y/o ceniza volante ( 16).La presencia de otras especies aniónicas en el sistema pasta de cemento-ambiente afecta a la capacidad de fijación química de los iones cloruros a las fases alumínicas (17-19).A continuación se pasa a describir el estado del conocimiento sobre la sal de Friedel, en aspectos relativos a su estructura, mecanismos de formación, estabilidad y caracterización. ESTRUCTURA DE LA SAL DE FRIEDELLa sal de Friedel y varios aluminatos y ferritos hidratados relacionados con él, pertenecen a la familia de los hidratos tipo AFm (5,20

In this work, a neuro-fuzzy (NF) simulation study was conducted in order to screen candidate reservoirs for enhanced oil recovery (EOR) projects in Angolan oilfields. First, a knowledge pattern is extracted by combining both the searching potential of fuzzy-logic (FL) and the learning capability of neural network (NN) to make a priori decisions. The extracted knowledge pattern is validated against rock and fluid data trained from successful EOR projects around the world. Then, data from Block K offshore Angolan oilfields are then mined and analysed using box-plot technique for the investigation of the degree of suitability for EOR projects. The trained and validated model is then tested on the Angolan field data (Block K) where EOR application is yet to be fully established. The results from the NF simulation technique applied in this investigation show that polymer, hydrocarbon gas, and combustion are the suitable EOR techniques.