This paper was also presented as SPE 106593 at the 2007 SPE Latin American and Caribbean Petroleum Engineering Conference held in Buenos Aires, Argentina, 15–18 April 2007.
Production of large volumes of water, coupled with production of formation sand and fines from oil and gas wells, often curtails the potential production of hydrocarbon. It is therefore highly desirable to decrease the volume of water and mitigate the solids produced from producing wells. Water and sand control generally have been addressed as separate problems with different treatment solutions. This paper discusses the development, and presents the field testing results, of a 2-step process that combines both water- and sand-control treatments into a single treatment.
Laboratory experiments were performed to examine the impact of these combined treatments. The relative permeability modifier (RPM) treatment results in water permeability reduction with little or no reduction in permeability to oil. Treatment with a consolidating agent transforms the unconsolidated formation sand and/or loosely packed proppant into a cohesive, consolidated, yet highly permeable, pack. The combined process has been field tested successfully. Results from field tests have shown that this process helped reduce on average 50% of water production, effectively eliminated the production of formation sand, and allowed the wells to withstand high production flow rates.
Both water production and sand production are a major concern in the petroleum industry because they are the most costly problems affecting hydrocarbon production rates. It has been shown that water production impacts the tendency of sand production.1 A recent study performed by Wu et al.2 showed that the effect of water cut on perforation failure and sand production is most significant for sandstones with high clay content.
Many oil wells produce a gross effluent comprising greater than 80% by volume of water. As a result, most of the pumping energy is expended in lifting water from the well, after which, the effluent must undergo an expensive separation process to recover water-free hydrocarbons. Disposal of the remaining water is also a troublesome and expensive process. For these reasons alone, it is highly advantageous to decrease the volume of water produced from oil and gas wells. In addition, however, decreasing the flow of water into the wellbore can help lower the liquid level over the pump in the wellbore and reduce backpressure in the formation to improve pumping efficiency and net daily oil production.
Another expensive byproduct that often accompanies oil and gas production is the production of formation sand and fines particulates, which is often preceded by water intrusion. Once water production begins, cementation between formation sand grains can deteriorate, allowing the formation sand and fines to migrate, or produce, with the production fluids. The higher the flow rates, the worse the problem. Fines migration often causes formation damage as pore channels or flow paths become plugged with fine particles. The wellbore can become filled with formation sand, choking off the production flow path and often requiring workovers to remove the sand fills. Formation particulates produced with production fluids can also destroy downhole and surface equipment.
These unwanted byproducts of oil and gas production have typically been addressed as separate issues requiring separate treatment solutions. Water control or conformance has been addressed by numerous studies.3–6 Plastic or resins were applied in consolidation treatments for sand control starting in the 1940s.7,8 The system described in this study offers a fresh approach for attacking both water and sand production problems at their source, using a single two-step process. It provides a viable and cost-effective treatment plan for reducing water and solids that can result in significant savings in time and production cost during the life of the well.
The chemical systems that are suitable for reducing or controlling water production in this study are nonsealing systems. They allow the flow of fluids through a porous medium even after the treatment. These non-sealing systems are typically dilute solutions of water-soluble polymers. They reduce effective water permeability by means of a "wall effect" by polymer adsorption onto the formation,9 creating a layer of hydrated polymer along the pore throat that inhibits water flow without substantially reducing the flow of hydrocarbons (Fig. 1).