Integrated Approach for Sand Management: Field Application to an Offshore Oil Field
Authors: Oshita Toshiya , Hirokawa Shoji , Rammah A. Aziz Y. 
Published: December 2007

This paper presents the sand management strategy for newly drilled wells including horizontal producers. To evaluate a maximum drawdown pressure that can be achieved without sand production is a key issue in the said management. If that drawdown would allow to produce at a desired rate, no active sand control method is used. However, estimating this critical drawdown pressure is one of the most difficult aspects in the production engineering. To obtain reliable estimation of it, integrating all the data available such as logs, core analyses and field production history, a procedure of the sand strength analysis has been established. Case studies reported in this paper could clearly identify the possible sanding zones. Based upon this information, then, the completion/perforation scheme that could gain the target oil rate without sand production was determined on each well. It is finally concluded that the sand strength analysis be a useful tool in selecting the optimum completion scheme in terms of the sand control.

Introduction

It was in 1961 when the first producer in the oil field located offshore of the ex-neutral zone between Saudi Arabia and Kuwait was put on stream and since then sands have been observed on some of the wells, though any fatal situation has not been encountered because the amount of sand production from each well is still small. As widely recognized, sand production would normally be accelerated by both depletion of reservoir pressure and increase in water cut. In this oil field, the reservoir pressure has been, and will probably be, maintained at a relatively high level by a strong water drive. However, it has been noticed that a pressure sink exists in part and will become lower as the oil production goes on. Besides, the production water cut will continue to increase with more and more water encroaching into the reservoir. Taking these two performances anticipated into consideration, it is reasonable to say that the sand production could become one of the serious operational problems in the near future. Therefore, as part of the reservoir management in this oil field, necessity of investigating a possibility of the sanding has been emphasized so as to propose some measures for the design of well completion and/or production facilities.

The best way to control sand production is to stop the sand at the reservoir. Otherwise, tubing, flowline and surface equipment such as production separator would easily be eroded and worn out in a short period, resulting in expensive repair. In a well where the sand production is anticipated, some measures for the sand control have to be scheduled prior to putting it on production. Generally, two types of method are considered; i.e.,natural completion below a critical drawdown pressure, andactive sand control by gravel packing, sand screens, etc.

Needless to say, active sand control is costly in terms of both initial cost and maintenance. Furthermore, productivity of the well might extremely be reduced due to high skin by these methods. Natural completion is, therefore, preferable wherever it is feasible.

Accordingly, in this paper, the following sand management strategy is applied to newly drilled wells including horizontal producers: "First of all, evaluate a maximum drawdown pressure that can be achieved without sand production well by well. If that drawdown would allow to produce at a desired rate, no active sand control method is used. On the other hand, if a higher rate is needed, active sand control should be considered."

This policy contains, however, one of the most difficult aspects in the production engineering; i.e., estimation of the critical drawdown pressure at and below which sands would not produce. To challenge this problem so as to obtain a reliable estimation of it, sand strength analysis is of greater importance, for which many sand failure models have been published with their field applications. P. 537^