Studies of a New Process to Consolidate Oil Sands With Plastics
Authors: Treadway B.R. , Brandt H. , Parker P. Harold 
Published: December 2007

A new three-step sand consolidation process has been developed which consists of

- injecting epoxy resin,

- following the resin by diesel oil to establish permeability and

- injecting an activator flush to polymerize the resin.

The process was developed in extensive laboratory research, proven in field applications in the Gulf Coast and California and is in routine use in those two areas with a success ratio of about 80 per cent. The first application was performed in April, 1962. At present, the process is being applied from 10 to 20 times per month. Loose sand similar to Gulf Coast formation material was consolidated in the laboratory at temperatures up to 200F and overburden pressures up to 4,000 psi. The consolidated sand had compressive strengths ranging from 3,000 to 12,000 psi and retained 50 per cent of its original permeability. The consolidated sand maintained strength in excess of 1,000 psi after exposure to boiling brine for one year.

Introduction

Sand control has been an oil industry problem for many years. Gravel packs, special liners and plastic consolidation have been used with varying degrees of success. The advantages of gravel packs and liners are relatively low cost and ease of application. Disadvantages are high susceptibility to plugging by formation fines and their tendency to complicate multiple completion operations when they are installed in a wellbore. Plastic sand consolidation has advantages over gravel packs and special liners. Because the formation adjacent to the wellbore is consolidated, formation fines are prevented from flowing. Furthermore, the outer perimeter of a typically consolidated formation is larger than that of a gravel pack or of a prepacked liner so that plugging of the outer perimeter is reduced. Disadvantages of plastic sand consolidation are its relatively high cost, difficulties associated with injecting resin uniformly over the producing interval and complexity of handling chemicals at the well site. Several sand consolidation processes have been described in the literature, but few of these processes meet all desired sand consolidation characteristics. This paper describes a new three-step process that meets the desired characteristics. Included are process description, discussion of laboratory experiments used to develop and evaluate the process and experience obtained from field applications.

Process, Resin and Consolidated Formation Characteristics: Process Characteristics

The sand consolidation process described in this paper and in recent patents is called a three-step process because there are three principal process steps consisting of

- injecting resin,

- establishing formations permeability and

- activating the resin to consolidate the formation.

Depending on its condition, additional steps may be necessary to prepare the formation for consolidation. For example, connate brine and crude oil should be removed from the axes around the wellbore. To accomplish this, diesel oil is injected into the formation to displace most of the formation crude oil and brine. The diesel oil is followed by a fluid that removes the residual brine and remaining crude oil. To do this effectively, the fluid should be miscible both with brine and with crude oil. Acetone, alcohol or low molecular weight aldehydes and esters are examples of such a fluid. In the present process acetone is used. Because acetone is a solvent for the epoxy resin, the acetone, in turn, is displaced by diesel oil. The formation around the wellbore is now saturated with diesel oil and is ready for the resin. The resin is a polar material that wets the formation sand preferentially to diesel oil. This wetting characteristic, coupled with high resin viscosity, enables the resin to displace diesel oil from the formation sand to be consolidated. The resin has a viscosity of about 150 cp at formation temperature, compared to a viscosity of 2 to 3 cp of diesel oil. Because of the high resin viscosity, the resin must be injected slowly to maintain pressures below fracturing pressures. These low injection rates also were found to be beneficial to complete wetting of formation sand. Because wetting is an essential step in adhesive processes, low pumping rates are maintained even when fracturing pressures would permit increased injection rates. The resin injection rate is 1/2 bbl/hour/vertical ft of formation to be consolidated.