Practical Approach to Effective Sand Prediction, Control and Management
CHAPTER ONE
Objectives and Significance of Study
The objectives of this study are as follows:
- To review state of the art sand prediction, control, and management
- To develop effective methodology for sand prediction, control, and
- To develop a step-by-step practical approach to sand prediction, control, and management.
CHAPTER TWO
THEORETICAL BACKGROUND OF SAND PREDICTION, CONTROL AND MANAGEMENT
Introduction
Sand production is a problem encountered during the production of oil and gas especially in formations relatively young in geologic age. These rocks are unconsolidated and accounts for majority of the world’s reservoirs, therefore most formations are susceptible to sand production. It can be defined as the production of quantifiable amount of sand particles along with reservoir fluids. Sand production is a two-part decoupled phenomenon: sand must be separated from the perforation tunnel (failure), and the flowing fluid must transport the failed sand. Stress, controlled by drawdown and depletion does the first, and rate, also controlled by drawdown does the second (Venkitaraman et al., 2000). Depletion and drawdown fail the medium under either shear or tensile or volumetric failure mechanisms or a combination of them (Nouri et al., 2003). The production of formation sand might start during first flow or later in the life of the reservoir when pressure has fallen or water breaks through. Sand production can erode downhole equipment and surface facilities, production pipeline blockage and leakage, generate additional need for waste disposal which could be a problem in areas of stringent environmental regulations, lead to formation subsidence in severe cases and generate more frequent need for workovers and well intervention. These effects can be viewed as economic and of safety hazards in the oil and gas industry.
Sand Production Effects
The effects of sand production are often detrimental to the productivity of a well in the longrun. Downhole equipment might be blocked or damaged and/or surface facilities disabled.
- Erosion of downhole and surface equipment: sand produced with formation sand at high velocity can erode surface and downhole equipment leading to frequent maintenance to replace such equipment. Blast joints, tubing opposite perforations, screens or slotted liners not packed in the gravel pack installation are potential sites for downhole erosion. If the erosion is severe or occurs over a sufficient length of time, complete failure of surface and/ordownhole equipment may occur, resulting in critical safety and environmental problems as well as deferred production. High-pressure gas containing sand particles expanding through the surface choke is the most hazardous situation. For some equipment failures, a rig assisted workover may be required to repair the damage (William and Joe, 2003)
CHAPTER THREE
EFFECTIVE METHODOLOGY FOR SAND PREDICTION, CONTROL AND MANAGEMENT
Introduction
Sand production is a problem encountered in most fields producing from unconsolidated reservoirs. It has been established that asides the natural tendencies of these formations to produce sand due to less compaction other factors come into play. These include pressure depletion, degree of loading and unloading, and water breakthrough. Tackling the problem of sand production entails the integration of sand prediction, control and management a shift of paradigm from just looking at a section. This ultimately involves team work of the drilling, completion, reservoir and production engineer, through best field practices. Getting right the sand prediction cannot be overemphasized as it forms the basis of well optimization in terms of overall cost and productivity. Sand prediction can be likened to a decision tool which directs the choice between sand control (exclusive) or sand management (passive). Depending on the tolerance risk of sand production in a particular reservoir the choice of sand management is made. Consolidated and friable reservoirs experience sand production latter in the productive life of the reservoir relative to unconsolidated formations where sand production is experienced early. Therefore it is essential to understand the characteristics of the formation before deploying/implementing a sand control or management technique. The new methodology of alleviating sand production focuses on using drilling operation, correlating between available prediction methods, using accurate data with little uncertainties in sand prediction.
CHAPTER FOUR
STEP-BY-STEP PRACTICAL APPROACH TO SAND PREDICTION, CONTROL AND MANAGEMENT
Step-by-Step Sand Prediction, Control and Management
Sand issues should be considered during the exploration and appraisal stages of a reservoir to identify productive intervals with the potential to produce sand. Depending on how severe the sanding potential is the choice of either sand control or management is made. It is important to bear in mind the whole concept of sand prediction, control and management in making field development decisions. Sand prediction affects the overall field or well development plan, hence recovery. Figure 4.2 depicts the application of sand prediction as a basis for major activities done for reservoir development. This chapter addresses the methodologies highlighted in chapter three. Table 4.3 presents fourteen steps developed as guide to ensure effective sand modeling process for reservoir development.
CHAPTER FIVE
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS
Summary
The objectives of this study are as follows: (1) to review state of the art sand prediction, control, and management techniques. (2) to develop effective methodology for sand prediction, control, and management. (3) to develop a step-by-step practical approach to sand prediction, control, and management.
In order to achieve the objectives mentioned above, in chapter two of this study various sand prediction, control, and management techniques were discussed. From chapter two the main types of prediction method are empirical, analytical, numerical and laboratory simulation. These techniques are to be integrated to effectively predict the sanding potential of a formation. Developed effective sand prediction methodologies were presented in chapter three, with emphasis on formation strength identified to be an important parameter in prediction. The decision between sand control (exclusive) and sand management (passive) is identified to be dependent on sand prediction. This makes prediction important in field or well development. Sand control selection methods and sand management methods were also presented in chapter three.
Knowing the sanding potential of a formation helps reservoir management. Chapter four provides step wise procedure to carryout sand prediction, control, and management. Also presented are flowcharts and screening criteria to help select candidate well for sand control. Extensive data acquisition and planning is significant in sand production management. The importance of this is captured in chapters 3 and 4 of this study. Deciding between sand control and management starts with prediction which must be treated carefully as mistakes could cause well loss.
Conclusions
Based on the theoretical studies and practical observations made from this study, the following deductions and conclusions are made:
- Integrating sand prediction, control, and management is key for well or reservoir optimization.
- The integration of sand prediction methods gives a better evaluation of the sanding potential and practical knowledge of the formation sand production
- Sand Management strategy has economic implications through rigorous well and facilities monitoring as well as sand disposal.
- A step-by-step procedure for effective sand prediction, control and management has been developed.
- Quantifying uncertainties in sand prediction will further boost the level of confidence in implementing results in reservoir development and sensitivity analysis helps in future
Recommendations
Based on the scope of this study the following recommendations are proposed:
- Since formation strength is an important parameter in sand prediction, methods that can measure this parameter in-situ should be developed to aid
- Further work can concentrate on developing a decision tree with economic implications and probabilities of success of the step-by-step procedure
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