Process of consolidation of an underground formation.

The present invention relates to a method for strengthening a subterranean formation. The present invention relates in particular to a method for strengthening portions of a subsurface formation surrounding a well or a borehole penetrating the formation.

Subterranean formations comprising fluids such as hydrocarbon fluids (oil and/or gas) or water which are recovered by the well penetrating such formations, often include unconsolidated granular layers or incompletely consolidated.

Such grains (also called hereinafter sand or sand particle) will be stripped of the layers by the fluid that will flow into the layers to the well and very likely will block the passages of wellbore fluids and/or the surface equipment communicating with the well, the piping of the DHW may well be locally damaged by the erosive action of the sand carried by the fluid stream which impinges on its walls.

It has already been proposed many consolidation techniques for such subterranean formations producing sand and it has been found that a number of these techniques were valid in this field.

The consolidation agents which are used in these techniques are very different compositions: as various types of resinous materials, compositions orthosilicate, carburizing materials such as aluminum oxide, and silicon halide compounds.

the present invention relates in particular to consolidation treatments using compounds of silicon halide as consolidating agent. This s at its agent have been found to be easy to use in this field. By the. means:

simple injection technique, the silicon halide compound may be injected through the well into portions of the formation to be treated, in gaseous form or in liquid form.

It is indispensable that it-Y has water around contact points adjacent grains of sand in the portions of the formation in which the silicon halide compound is injected. The following reaction will arise:

^ + SiCEl>si0 2:00 - GB₂ 4:00 C1 +,

The amorphous silicon dioxide formed by this reaction will bind the grains of the forming assembly, thereby increasing the resistance to compression portions of the formation. It may be noted that in order to maintain sufficient permeability portions consolidated formation, the presence of water in a small amount is needed.

A finalization processing the formation where a silicon halide compound in liquid phase is passed through portions to be treated formation, is described in U.S. Patent no. 3 * 055.426 (inventors: Kerver, Holland and Haken; recorded "5 February 1959" admitted 25 September 1962).

Therapy wherein the silicon halide used as consolidating agent is injected through '.. the formation in gaseous form, as described in English

no. 1.536.209 (inventors: Meijs and Davies; recorded 12 March 1976, accepted 19 October 1978).

As it has already been noted above, it is essential that there is water around contact points grains of sand formations which are to be consolidated using a silicon halide compound. In the formations where the surface of the sand grains is coated with oil, a pre-processing should be performed for the surface of the sand grains is preferably wetted with water.

Such treatment is described in U.S. Patent no. 3.055.426 (inventors: Kerver, Holland and Haken; 5 February 1959 recorded " admitted 25 September 1962). This change is obtained by treating the surface of the sand grains with a suitable surfactant.

The majority of subterranean formations which are to be treated for consolidation have however the pore walls wetted water and can therefore be treated directly by means of a consolidating agent consisting of silicon halide. Such formations, or already includes water adherent to the pore walls, or can easily be wetted by injecting water inside by the P|beds or the borehole, water enters then the portions of the formation to be consolidated, too much water in the pores of such formation may result in an undesirable reduction of the permeability after the consolidation. Before injecting the consolidating agent, the amount of excess water must be removed from portions of the formation to be consolidated by injecting a dry gas through the pores (in the case of a formation containing gas) or a non-polar liquid (in the case of a formation containing a liquid). It should select the volume of fluid that will excess water, so that there remains a sufficient amount of water on the walls of the pores of the formation to form a consolidating without causing an undesirable decrease in permeability.

the use of the compounds of silicon halide as consolidating agent is particularly advantageous in that by then wire;

does not require pretreatment of the formation to remove all water pore portions of the formation to be treated, such as required in almost all other operations consolidation. In these operations, the presence of a film of water on the surface of the particles of the formation prevents the consolidating agent from sticking to the surface of the particles, resulting in low consolidating. Removing water from the surface of the wet particles of the formation is expensive and experience has shown that it is difficult to conduct with efficacy necessary. It may be noted that it is desirable to use a consolidating agent which reacts with water present around the contact points adjacent grains of sand. Such an agent can be forced into the formation using a simple operation that can be performed at a relatively low cost.

A detailed study of samples from a formation wetted with water treated with a gas mixture of nitrogen and détrachloruresilieium reveals that, although the grain samples are bonded with a cement siliceous (SlO ^), - an 'increase the compressive strength of 1' sample was necessary. Must be indeed that the portions of the formation consolidated around the wells have a high compressive strength when the well is producing fluids under high load conditions, since under such conditions, the grains of sand from. parts of a formation are poorly consolidated succaptibles separate from with the formation and cause damages in the well and/or equipment ^ ^ ^ U-e_ceainunif """ T-àvee the well.

An object of this invention is a consolidation method portions of a subterranean formation permeable wetted with water and containing liquid, the formation surrounding a well penetrating the formation. The method comprises forming a TiN halogâaure composed of silicon on a water layer adherent to wet walls of water pore portions. the formation. By this method allows a high compressive strength portions consolidated.

The method according to the invention comprises the step of pre-processing to the acid component sheets at least every pore wall portions contigSes at well. A suitable acid in this case is the aeide hydrochloric.

To explain in more detail the method according to the invention, 5 experiments and testing will be described below from examples. Area by an simplicity, all SAL experiments are based on the following standard frame processing:

Standard frame processing.

A glass tube 36 mm in diameter and 12 cm long is filled with sand from the region of the south-west of AMPA in the state Brunei. The sand particles selected have dimensions of between 200 and less 2 .le sand from sand filters used in production facilities of gas from the region of the south-west of AMPA.

Before placing the sand in the tube, the sand grains are wetted by a uniform current tap water passing over their surface. The amount of water being equivalent to 5 $weight of the sand.

The sand accumulated in the tube is then solidified. passing a gas mixture of CLC ^ and NG. The weight of CLC " 4 is 2496 and that of ng 7 β ^ · the flow rate of the gas mixture is 61/per minute (the flow rate being calculated at the tube inlet.).

- The sand is processed by the CLC ^ diluted during 10 min, the tube is then broken and the consolidated sand is cut transversely into 5 equal parts of 3.6 cm each. The parts are numbered consecutively beginning with 1 5 to the inlet of the tube. The resistance of the samples is then determined in accordance with the hardness testing apparatus of tan Brine 11.

The apparatus used to measure the coefficient of BH (BHN) is described A.C. - der Vlis join "Glassification rocks by simple hardness test" presented to the second congress company International mechanics Hun in September 1970.

The hardness given in table has result from the application of the standard treatment at a temperature of 293° Kelvins (20 °c) under a pressure of 1 bar gauge.

Results are obtained substantially equal to those of the array by applying the standard treatment at a temperature of K-373° (100 °c) and a pressure of 150 bar.

Experiment 1_{the V:}

In this experiment, injecting the mixture of CLC ^ and (in the proportions by weight of CLC 24 $76 $and ^ n_grams ) of the standard treatment, is preceded by pre-treatment of the sand.

During this pre-treatment, a gaseous mixture of CLC ^ and kg (0.84 $in the proportions by weight of QCIS. ^ and 99.76 $n_grams ) is sent through the sand during 25 minutes rate^:

unitary 61/min. The amount of CLC ^ contained brood gas mixture is 1/100 of the amount of CLC ^ used during the step of consolidating the standard treatment.

The Brinell hardness test (see table 1) established at the end of experiment 1 shows a significant increase of L_has compressive strength of various parts of the agglomerate ' sand in comparing the results of the array.

the increase ratio values of Brinell hardness resulting from a step of pretreating the surface of the grains by hydrochloric acid resulting from reaction of the CLC ^ on the water present around grains of sand. Since the CLC ^ is injected in a small amount during the period of pretreatment, the total amount of CLC ^ can react after this period has ith water adherent to grain-sand which are located at the entrance of the formation, the HCl vapor caused by this reaction is carried by the nitrogen gas in the pores between the grains of sand to consolidate and is dissolved in water adhering to these sand grains, cleaning their surface so that the amorphous silicon dioxide formed during the reaction can strongly adhered and bond the sand particles together to form a mass having high " compression.

■to verify the theory set forth above, i.e. 1' cleansing action performed by the HCl produced during the pretreatment, the experiment suivantè ^ is conducted:

2 Æxpérienca

By this experience, 6n studies the influence of hydrochloric acid on the compressive strength of the agglomerates of sand consolidated. In this experiment, the step of consolidating the standard treatment is preceded by a pre-treatment using an aqueous solution containing 15# weight of HCl. The solution is passed through the sand as in the standard treatment, thereby displacing water from the surface of the sand grains. Then injected nitrogen gas through the packet of sand to move most of the solution until it remains at the grain surface an amount of solution equal to #5 weight of the sand. The standard processing is '" then applied and the test of Brinell hardness gives the results of table 2 .'

Table 2

BHN sectional (kilograms/mm.² )

1, 3.9

2, 3.7

3, 3.9

4, 4.4

5, 3.9

This experiment is conducted under the conditions of temperature and pre ssure s at ambient.

In the experiment 2, the side of the section 1 located

to the inlet of the tube has a hardness value greater than is Briftell is measured at this point when the results of the experiment Tj and this hardness is substantially equal to the value of Brinell hardness measured at the other end of the section 1 in the experiment 2"

Since the section side 1 located at the inlet of the tube has not been in contact with hydrochloric acid in the experiment 1 as has been the case in the experiment 2, it can be concluded that it is the preprocessing by the HCl which has improved the quality of the consolidation.

Experiment 3

In the experiment 1, the sand grains are pretreated for 25 min avee hydrochloric acid provided by the reaction of silicon tetrachloride with water present on the sand grains. Then, the sand is consolidated by the application of the standard treatment * to better determine the time required for pretreating the sand, a series of experiments the type of experiment 1 are carried out. During these experiments have changes the time exposure of the sand grains to acid provided by the reaction between the SID ^ and water. Thus the gas mixture of SiŒL ^ and in the proportions of 0.24 $weight, CLC ^ and 99>76 $of is injected through the sand at rate of 61/minute for different durations. The standard processing is then applied. The results are given in table 3.

Table 3

duration of the willwill prétrai -

(minutas) equipped working

0

4

6

8

10

13

:: 24

average value of the OCG 4001 BHN/mm.² ) 2.5

2.5

2.5

2.5

3.5

4.5

4.5

(1) the value of the BSN given is an average of values BHN

5 ·℮η portions of which the packet of sand was cut after consolidation.

(2) experiments are conducted under ambient conditions, temperature Wt of pressure.

It is found that an increase of the resistance is observed for processing times less than 8 min. Between 8 and 13 min, there is - a rapid increase in resistance. The processing time greater than 13 minutes are not give, in this case, better results.

^ Experience

■■^ the method described in experiment 3 is repeated but under a temperature of 373° k (100 °c) and a pressure of 150 bar, instead ambient conditions previously used.

The results are given in table 4.

Table 4

of pretreatment

(min

Average value of the BHH (kilograms/mm. ^)

O

5

1Ô

24

2.5

5.0

5.0

5.0

Under these conditions of elevated temperature and pressure_T- the time it takes for the hydrochloric acid product may act upon the sand to produce optimum results is less than 5 mins. This duration is significantly reduced in comparison with the time required to obtain the optimum results at ambient conditions of temperature and pressure of the experiment 3.

Experiment 5

This experiment is conducted, as in the standard treatment, on the agglomerate of sand. However, there is, in this experience oil in place of the gas in the pores of the heaps of sand.

This oil is displaced by a condensation product of a mixture of hydrocarbon s having a volatility equivalent to the session in gasoline. Since the surfaces of the sand grains are wettable & water, there leaves a film of water, in an amount equivalent to 5 $weight of the sand. Then perform pretreatment using an acid, the condensation product is removed from the pores by injecting a volume of nitrogen gas.

In this pretreatment, the hydrochloric acid is used as gas, it supplied through pores in the agglomerate of sand by an inert gas (such as nitrogen) at rate of 61/min.

The rate is calculated on the internal surface of the section ^ of the glass tube. The mixture tetrachloride silicrun and c.¹ nitrogen Tooling then injected through the sand as described in the standard treatment. The following Brinell hardness values are measured (see table 5)*

Table 5

Sectional bhïï (6mrn/kg.² )

1, 4.0

2, 3, ℮

E 4.3

4, 4.0

5, 3.9

(fctte experience, is meaée challenges ambient conditions TEM pérature and pressure.

In previous applications of a consolidation process using silicon tetrachloride into a gas producing formation by a carrier gas (nanograms), it is customary to rapidly consolidate the formation by injecting the silicon tetrachloride at rate of 10 liter/min, the production wells treated indicates however that the sand n * a not consolidated in optimum manner as the left expect results when simulated in the laboratory experiments.

- To verify inefficiency consolidation treatment, the present invention proposes to conduct the following test:

Ûtesting.

during this test, a pretreatment is applied to portions of the formation to be consolidated. In the pretreatment silicon tetrachloride is injected for a period of 30 minutes. low-rate: 0, X->grams to verbs " ^ if? / mittaté temperature, and normal pressure.

the QCIS ^ is mixed with a carrier gas: ^ Ν · this carrier gas mixture 2, 2jé\du eStiégaie le to the weight of the mixture, the low injected at the j ^ DS rate * # ' INAs ^ / min * the amount of CLC ^ contained

flow rate D * injecting silicon tetrachloride able to react with the water which is already present in the pores of the formation, producing the âifiiiHCOL which is dissolved in the water adherent to grains Sabledes portions of the formation to be consolidated.

Apràs to " pretreatment, injects a mixture of chloride of silicon and nitrogen gas at higher throughput of & 1' order of 0.7 ^ ^ ^ X preferably Lo of Ag/miatits for SiŒL ^ ^ and/minmin.pour 26.8 nm. the FGs under normal conditions of temperature and pressure " the amount of SiGL ^ 24 $represents the weight of the mixture. The period of consolidation hard 150 minutes while the 30 minute pretreatment period lasts. During the production period which follows, it appears that the well does not weathered consolidating.

In short it may be noted that the present invention relates to the forming pores of a pretreatment with an acid in gaseous or liquid form, to increase the aggregate strength of silicon dioxide produced during the consolidation process of the formation during passage of a composition of silicon-halogen in gaseous or liquid form through the formation.

The hydrochloric acid can be injected directly into the formation, or can be produced, for example by injecting slowly a composition of silicon-halogen in the formation.

Outside of hydrochloric acid used in the experiment 2 for pretreatment portions of the formation to be consolidated, one can employ other acids such as sulfuric acid, hydrofluoric acid, formic acid, citric acid, phosphorous acid or e · ¾..., or blends of these products in gaseous form, transported by a carrier gas or; liquid form or dissolved in a carrier liquid. The results are comparable to those obtainable with the aeide hydrochloric.

It is preferred, however in most cases the use of HCl due to the low cost and high availability of the cilia of this acid. May be used, in solution in water as carrier, amounts of HGl between 1 $40 $and the weight of the solution.

It may be noted the fluids (gas or liquid) used for transporting the compound silicon-halogen must be "dry", i.e. that it should not contain a quantity of water greater than can react with 10 $by weight of the composition silicon-halogen injected.

In addition, any excess amount of water in the pores of the portions of the formation to be treated must be removed by passing through the formation, a gas having a low water vapor content or a non-polar liquid such as a condensate comprising a hydrocarbon mixture having a volatility equivalent to that of gasoline.

Amount d *•if the water in the pores is insufficient for the needs of the consolidation, a gas containing a mist of - water particles. is sent through the formation. One may also place a water stream through the formation before the passage from * a gas having a low water vapor content ' or the non-polar such a condensation product.

. Currents of inert fluids may be sent through the pores of the formation between the batching fluids subcontractors (including the fluids used for the control of the amount of water contained in the pores).

•if 1' acid is not compatible with the consolidation process which is to be subsequently applied, should be removed this acid using a suitable fluid jet, prior to injection of the consolidating agent.

Outside the silicon tetrachloride used in the standard treatment, the experiments and testing, other compositions of silicon-halogen such as silicon hexachloride, 1 * octochlorüre silicon, silicon fluoride may be used with equivalent results.

the composition * silicon-halogen can be injected at any - concentration is, as needed. The weight the tetrachloride injected during the consolidation treatment and the pretreatment is between 5/1 and 500/1.