ABSTRACT: 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, frae 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 (Ledlow 1985, Suman 1975) by minimizing the damage caused by the completion. Despite these efforts experience has Houchin 1988) 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 (Hoven van Genderen 1992). 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 years that applying relatively large volumes of gravel at above fracture gradient pressures followed by a internal gravel pack have resulted in less damage and good productivity improvements (Liebach 1967). 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" (Hannab 1993).
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 (Hainey 1992). 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 (Bale 1993) and, as described in this paper, in the Gulf Coast of the United States and in the Far East.