Report Biannual Ogrindo

November 6, 2010 § Tinggalkan komentar

Abstract

Sand production is one of the biggest problem in oil and gas production. Sand can damage the surface and downhole facilities. Sand production simply occurs in unconsolidated formation. To overcome this constraint, mechanical and chemical method has been much developed. In this research chemical method based on epoxy resin is used to solve sand production. Epoxy will react with its hardener to polymerize thus able to bind sand grain with covalent bond.

In this research, artificial core is synthesized to represent real core in oil and gas field. Those artifical core has 2:1 sand and cement ratio. It will be immerse into epoxy resin to evaluate its mechanical properties with and without resin treatment.

Data indicates that its compressive strength increase by test using uniaxial stress. However its porosity reduce 20-40%. From observation it is obvius to conclude that core immersing with resin will strengthen matrix binding among sand grains..

Introduction

Oil and gas production more increase rely on market demand. Any statement to replace hydrocarbon fuel with vary alternative could not relieve people’s dependance on it. For that reason, many research were conducted to maintain its sustainability. Sand production as effect of poorly consolidated and unconsolidated reservoir is detrimental case on reservoir. It erodes tanks and pipe lines, increase maintenance cost, and lost oil production. Based on the observation, we conclude that sand problem could be solved by injecting the polymer to cement or to consolidate the sand grains. Hence it was not carried out together with oil production. Adhesive characteristics owned by the polymers are the key for the work.

After examining previous work, epoxy resin, furan resin and organosilane are mostly used resin to solve sand problem. Those resin enhance good attempt to obtain better result among others. Recent research depict epoxy resin as cementing agent for unconsolidated rock. Epoxy resin stand for epoxide resin and hardener. It is generally synthesized between bisphenol-A and epichlorohydrin those finally produced chemical compound with epoxide group. Hardener on this objective comes from compound containing amine group those react with epoxy to form covalen bond.

Epoxy resin has many advantages as main compound regard to sand problem. It is local product thus affordable and accessible. Beside that, it will create polymer with great stiffness and strongly bind due to crosslink structure. Moreover it is easy to work with epoxy, polymerization goes without additional reactant. Curing time and concentration of reaction are important variables to investigate its ability to solve sand problem. Furthermore resin and its hardener composition are significant to create best resin system.

Objective

The objective of this research is to evaluate epoxy resin in solving sand production on gas field without reducing much permeability and porosity. Consequently, it will enhance gas production. Sand grains is bind by resin with vary concentration and curing time.  .

Methodology

This research divide its work into two main parts, resin’ preparation and core test.

  1. Resin’ preparation

Epoxy resin play its role for this objective. It is well known as an adhesive polymer. Epoxy resin is mainly synthesized by reacting bisphenol-A and ephichlorohydrin. Its molecular structure enhance sand grains to bind together by covalent bond. Picture below depict reaction forming epoxy.

Epoxy needs any hardener to create epoxy resin system. Hardener would polymerize epoxy resin and time spent to undergo complete polymerization is known with curing time.  Epoxy and hardener 1:1 (ratio of volume) are mixed in beaker glass thus stirred in order to create homogenous mixture. Resin preparation was conducted on ambient temperature in humic acid. Curing time and reaction temperature are important variable which determine resin performance.

  1. Core Test

Artificial core (Figure 3) those representing unconsolidated core in oil and gas field are used for this purpose. Those core containing 80% sand and 20% cement with 2:1 (ISRM standard)2 height and diameter ratio respectively. On this research, those artificial core had 2 inch height and 1 inch diameter.

Artificial core was immersed into epoxy resin to investigate resin ability binding sand grains. Identical core, without resin treatment, was used as reference to compare core properties before and after resin treatment. Both of them are test towards uniaxial stress. Those core are compressed with high pressure until rupture. Before test conducted, core sample were saturated by reservoir fluid (formation water) for 24 hours.

Core test is continued with evaluating porosity of resins to investigate plugging effect due resin treatment. Porosity test were conducted with ultraporosity instrument.

Result and Discussion

Resin performance is examined by its concentration and curing time. It is done to create optimum atmosphere working with epoxy resin.

Those graph depicts resin viscosity for vary time. Escalation on viscosity told us that epoxy and its hardener is reacting. High viscosity will hinder resin to enter core. From those data, poymerization of epoxy occur since 4 first hour after epoxy is mixed together with its hardener. These data also explains that 1:1 percent volume ratio between epoxy and hardener impart fastly curing time and higher viscosity.

After examining resin’s behaviour regard to its viscosity and curing time. Resin’s optimum condition then used for artificial core. Result below indicates data obtained by immersing core into resin system. Data are classified into compressive strength and porosity data.

  1. Uniaxial stress test
Sample Compressive Strength (ton) 

Without resin

Compressive Strength (ton) 

With resin treatment

1 0.4 1
2 0.5 1.2
3 0.5 1.1
4 0.4 1
5 0.2 1

Table 1 : Compressive strength data

Table 1 shows compressive strenght data by test with uniaxial stress. From data above, it can be interpret that epoxy resin is definitely succesful to strengthend binding among sand grains. Core with resin treatment undergoes twice higher compressive strength than its reference. Core mechanical properties increase significantly by evaluating its compressive strentgth. However other variable are important to evaluate for supporting former data.

  1. Porosity evaluation

Examining core porosity will explain resin’ influence to artificial core regard to its mechancical properties beside compressive strength. Moreover this data will be other indicator to determine whether epoxy is worth to overcome sand problem.

Core sample Porosity (%) 

Without Resin

Porosity (%) 

With resin treatment

Porosity reduction 

(%)

1 27.2 17.8 34.5
2 29.7 21.3 28.3
3 29.8 21 29.5
4 30.9 18.4 40.4
5 31.5 23.8 24.4

Table 2 : Porosity data

This data shows that resin treatment will plug porosity reducing 20-30% for whole one. Porosity reduction will hinder fluid flow viscosity thus relieve its productivity. To overcome reduction in porosity, preflush is needed to clean out pore from rest of resin used. Preflush can be conducted with mud acid. But till this data is published, preflush was not done yet.

Conclusion

Polymerization between epoxy and hardener occur in the first 4 hour since the resin is combined. Moreover its best composition are 1:1(percent volume) because it results on fastly curing time and higher viscosity

Epoxy resin is succesfully binding sand grains. It can be examined from its compressive strength data with and without resin treatment for identical core. Core with resin treatment impart twice higher compressive strength than its reference. However it reduces core porosity 20-40%. For that reason, preflush with mud acid are needed to conduct, in order to enhance core porosity.

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