Field Experience With Chemical Sand Consolidation as a Remedial Sand Control Option
Authors: Kotlar Hans Kristian , Moen Arild , Haaland T. , Wood T. 
Published: October 2008

Sand production from wells is an ongoing challenge for the oil industry. In some wells intervention is required for remedial sand control or new sidetracks are required. However, for a limited number of suitable wells, chemical treatments that consolidate the near wellbore area can be a viable alternative to improve well offtake rates. Chemical sand consolidation can give a formation some additional residual strength in order to enhance the maximum sandfree rate (MSFR).

Sand production in weakly consolidated reservoirs will occur when stresses in the well/perforation tunnel walls are large enough to disrupt the binding between the individual sand grains. This will generate a plasticised layer of sand in the near well bore area. The layer will erode by the produced fluid and may be transported to the surface. The rate of erosion will depend on the residual strength of the plastified material and the fluid rate.

The chemical treatment developed to overcome these problems is environmentally acceptable with a low value for bioaccumulation and a high value for biodegradation. The chemical is mixed in diesel and bullheaded into the well allowing placement that can be complimentary to existing control measures. Once placed the active chemical components will react with the connate water in the near wellbore area and form a polymerized network which binds the sand grains together. In that way, the residual strength of the formation is increased and can withstand larger hydrodynamic forces (i.e. production rates) before the grains are transported into the wellbore.

The method has been employed in eight different StatoilHydro operated wells in four different fields, with encouraging results. Moreover, there are indications that water cut could be reduced due to the treatment. Combined with a higher draw down potential, this gives support for the use of the sand consolidation method as an IOR initiative.

Introduction

Sand production has many negative implications to oil production, and various techniques have been developed in order to stop the sand from being produced. The most common mechanical methods are installation of a screen or a slotted liner in the production interval of the well. This can be combined with a gravel pack [1-6]. Some wells are completed with a cemented liner and oriented perforations that will minimize the risk of sand production [7, 8]. Most of the above mentioned methods involve heavy hardware and tools and significant cost. An alternative way to minimize sand production is to run the well on MSFR or Acceptable Sand Rate (ASR). The well is choked back and the flow rate is reduced. However, although running on MSFR might be low cost, in implementation, it will be highly uneconomic with respect on ongoing revenue, especially if it runs at far below the well potential.

The prior art of chemical sand consolidation is to make "rock" from sand, in other words to increase the strength of the matrix to a large degree. This approach is also associated with a huge reduction in permeability. The basic idea of the present work is to only increase to the residual strength of the formation by a small amount in order to enhance the MSFR. This will have large economical implications in fields with wells controlled by MSFR, and particularly in the decline phase in which the field is controlled by the well potential.

Since these criteria for strength are quite low, the search for potential treatment chemicals could be carried out in areas completely different from the traditional chemicals used in sand consolidation. Unlike conventional chemicals for sand consolidation, the chemical found by screening and investigation is environmentally acceptable. Screening of chemicals and laboratory testing has been published elsewhere [9].