Method of coating core samples

• US 4,419,314 A
• Filed: 05/26/1981
• Issued: 12/06/1983
• Est. Priority Date: 05/26/1981
• Status: Expired due to Term

• Current Assignee: Core Laboratories LP (Core Laboratories NV)
• Original Assignee: Core Laboratories LP (Core Laboratories NV)
• Inventors: Bush, Darrell
• Primary Examiner(s): Parrish, John A.
• Application Number:
  US06/266,990
• Time in Patent Office: 924 Days
• Field of Search: 264/130, 264/139, 264/135, 264/264, 264/271.1, 264/279
• US Class Current: 264/130
• CPC Class Codes: B29C 39/10 incorporating preformed parts or layers, e.g. casting around inserts or for coating articles coating a surface by casting in general B05D1/30, B29C39/126 takes precedence
• CPC Class Codes: B29C 70/70 Completely encapsulating inserts B29C70/86 takes precedence
• CPC Class Codes: B29K 2063/00 Use of EP, i.e. epoxy resins or derivatives thereof, as moulding material
• CPC Class Codes: B29L 2031/40 Test specimens ; Models, e.g. model cars mannequins B29L2031/7028; Probes
• CPC Class Codes: E21B 25/08 Coating, freezing, consolidating cores E21B25/06 takes precedence; Recovering uncontaminated cores or cores at formation pressure

Abstract

A method of coating a core sample in which a distillate such as petroleum jelly is applied to the exterior surface of the sample. A cylindrical mold is partially filled with a plastic mixture of hardenable epoxy resin and hardener therefor, and one end of the core sample is slowly inserted into the mold under a pressure which preferably is not more than about 50 pounds per square inch. In some cases the inserted end of the sample is pre-coated with the plastic mixture. As the insertion of the sample is continued, the mixture flows up the side of the sample and covers the opposite end. The coating is cured by maintaining it in the mold at room temperature for a period of time sufficient to enable the resin to set up and then by holding it at an elevated temperature for at least about eight hours. Upon the removal of the coated sample from the mold, the ends are cut off to expose the sample material.

Claims

1. A method of preparing a geological core sample containing pore spaces and representative of an underground formation from which the sample is taken to prepare the core sample for testing in testing apparatus in which pressures are applied to the core sample to simulate approximate overburden pressure to which the sample material was subjected in its underground formation, the method comprising;

applying a petroleum based release material to the exterior surface of the core sample;

partially filling a mold with a plastic mixture of hardenable epoxy resin and hardener therefor;

inserting one end of said core sample into the partially filled mold, the space between said sample and the interior of said mold lying within the range of from about 0.010 cm. to about 0.050 cm, to form a plastic coating on said sample substantially free of voids and having a thickness within said range so that the plastic coating on the thus coated sample is sufficiently thick and stiff to prevent intrusion into the pores of the core sample during testing of the core sample under confining pressure yet is sufficiently thin to transmit the confining pressure to the sample;

applying a sufficient pressure to the opposite end of the core sample to slowly urge said sample into said mold until the plastic mixture therein covers the entire surface of said sample;

curing the plastic material for a period of time sufficient to form a stiff coating on the core sample;

removing the thus-coated core sample from said mold; and

cutting off the ends of the core sample to remove the coating from said ends.

2. The method of claim 1 which further comprises,

curing the coating on the core sample by maintaining the same at room temperature for at least about four hours and thereafter maintaining said coating at an elevated temperature for at least about eight hours.

3. The method of claim 1, wherein the pressure applied to the sample is not less than about 5 pounds per square inch.

4. The method of claim 1 further comprising:

grinding the ends of said coated core sample until such ends are flat and perpendicular to the axis of said core sample and the grains of core sample are exposed.

5. The method of claim 1 comprising flushing the core sample with an organic cleaning material prior to applying said release material.

6. The method of claim 5 wherein said cleaning material is selected from a group consisting of toluene and hexane.

7. The method of claim 1, wherein the coating is cured by maintaining the same at room temperature for at least about four hours and thereafter maintaining said coating at an elevated temperature for at least about eight hours.