WO2013096780A1

WO2013096780A1 - Method of using a non-acidic stimulation fluid in high temperature sandstone formations

Info

Publication number: WO2013096780A1
Application number: PCT/US2012/071261
Authority: WO
Inventors: Mohammed Nasser AL DAHLAN; Khalid Abdullah AL DOSSARY; Abdullah Mohammed AL HARITH
Original assignee: Saudi Arabian Oil Co; Aramco Services Co
Current assignee: Saudi Arabian Oil Co; Aramco Services Co
Priority date: 2011-12-23
Filing date: 2012-12-21
Publication date: 2013-06-27
Anticipated expiration: 2014-06-23
Also published as: US20130161012A1; US9334721B2

Abstract

A three step method of using a non-acidic stimulation fluid in high temperature sandstone formation is provided. The method consists of using a preflush brine, sodium hydroxide solution, and an overflush brine.

Description

PCT PATENT APPLICATION

METHOD OF USING A NON-ACIDIC STIMULATION FLUID IN HIGH

TEMPERATURE SANDSTONE FORMATIONS

INVENTORS: Mohammed N. A3 Da lan

Khalid A. Al Dossary

Abdullah M. Al Harith

Field of the Invention

[0001] This invention relates to a method for using a non-acidic composition to stimulate an underground petroleum or hydrocarbon bearing formation. More specifically, the invention relates to a method of using a sodium hydroxide containing solution to stimulate a sandstone formation at high temperatures.

Background of the Invention

[0002] During well operations, chemicals are often injected into the underlying formation in a process laiown as stimulation. Stimulation of the formation is one technique that can be used to increase the net permeability of a formation or reservoir. Some exemplary known stimulation techniques include: (1) injection of chemicals into the welibore to react with and dissolve conditions limiting production (e.g., the presence of clays and drilling solids); (2) injection of chemicals through the welibore and into the formation to react with and dissolve portions of the formation, or to create alternative flow paths for recoverable hydrocarbons (e.g. acid-fracturing or matrix-acidizing); and (3) injection of chemicals through the welibore and into the formation at pressures sufficient to cause fractures in the formation, thereby creating a flow channels through which hydrocarbons can more readily move from the formation into the welibore.

[0003] In particular, sandstone formations are particularly susceptible to formation damage from formation minerals such as clay and other siliceous deposits. Historically, acid, or acid-based fluids have been used in the treatment or stimulation due to their ability to dissolve both formation minerals and contaminants (e.g., drilling fluid coating the welibore or that has penetrated into the formation) introduced into the wellbore/formation during drilling or remedial operations.

[0004] The removal of formation minerals and other deposits, such as clays or drilling solids, are key concerns in well completion operations. The known prior art techniques noted above typically involve highly concentrated acids, such as hydrofluoric acid (HF) and hydrochloric-hydrofluoric acid mixtures, which are both highly corrosive and can create dangerous operating conditions.

[0005] One difficulty encountered with traditional sandstone stimulation operations that employ HF is that HF can precipitate into the formation, causing formation damage and limiting matrix stimulation treatment efficiency. The damage caused by the fluoride precipitations are aggravated by higher temperatures. Another difficulty encountered, with traditional HF sandstone stimulation is the acid reacts instantaneously with the formation, thereby limiting penetration of the acid into the formation. Therefore, it would be advantageous to use a stimulation fluid that does not form precipitants when it reacts with the sandstone formation at high temperatures and has a slower reaction rate.

Summary

[0006] The current invention provides a method for using a non-acidic stimulation fluid in high temperature sandstone formations. The non-acidic stimulation fluid is provided as an alternative to traditional stimulation methods that typically involve hydrofluoric and/or hydrochloric acids. The non-acidic stimulation fluid has a slower reaction time with the sandstone formation, thereby allowing for deeper penetration into the formation. Additionally, the non-acidic stimulation fluid does not form precipitations after reaction with the sandstone formation that can damage the wellbore upon further stimulation techniques.

[0007] In one embodiment, a method for stimulating a hydrocarbon containing formation using a non-acidic stimulation fluid is provided. The method includes involves three steps. In a first step, a preflush brine is injected into the sandstone formation. In the second step, a non-acidic stimulation fluid, is injected into the foundation. Finally, in the third step, an overflush brine is injected into the sandstone formation. In this embodiment, no other stimulation fluid is used. The method is operable to allow efficient and. effective penetration of the non-acidic stimulation fluid into the sandstone formation,

[0008] In one embodiment, the preflush brine is chosen from a group of haiide-containing brines. In certain embodiments, the preflush brine can be aqueous ammonium chloride. Preferred concentration of aqueous ammonmm chloride is in a range of between 5 and 10% by weight, more preferably in a range of 5-8% by weight. In other embodiments, the preflush brine can be potassium chloride. In a preferred embodiment, concentration of potassium chloride will be in a range of between 3 and. 8 % by weight, more preferably 4-6% by weight. In one embodiment, the preflush brine is injected into the sandstone formation first.

[0009] In one embodiment, the non-acidic stimulation fluid is a sodium hydroxide solution. In certain embodiments, the concentration of the sodium hydroxide solution is in a range of between 5 to 28% by weight. In one embodiment, the sodium hydroxide solution is injected into the sandstone formation after the preflush brined. In one embodiment, the non- acidic stimulation fluid is only sodium hydroxide solution. In this embodiment, no acid stimulation fluid is used. In another embodiments, the non-acidic stimulation fluid is a potassium hydroxide solution. In certain embodiments, the concentration of the potassium hydroxide solution is in a range of between 5 to 28% by weight. In certain embodiments, the potassium hydroxide solution is injected into the sandstone formation after the preflush brine.

[0010] In one embodiment, the overfmsh brine is selected from a group of halide- containing brines. In certain embodiments, the brine can be aqueous ammonium chloride in a concentration range between 5 to 10% by weight, alternatively between 5-7%, 7-9% or 9- 10% by weight. In one embodiment, the overfmsh brine is injected into the sandstone formation third.

[0011] In certain embodiments, high temperatures are advantageous to increase the efficiency of the non-acidic stimulation fluid. In one embodiment, the non-acidic stimulation fluid is preheated in a range between 20°C to 70°C before injection. In certain embodiments, the non-acidic stimulation fluid is allowed to react with the sandstone formation for between 3 to 24 hours. In other embodiments, the temperature of the sandstone formation can be used, to heat the non-acidic stimulation fluid after injection. In certain embodiments, the non-acidic stimulation fluid is allowed to react with the sandstone formation for between 3 and 24 hours.

Detailed Description of the Invention

[0012] Although the following detailed description contains many specific details for purposes of illustration, it is understood that one of ordinary skill in the art will appreciate that many examples, variations and alterations to the following details are all within the scope and spirit of the invention. Accordingly, the exemplary embodiments of the invention described herein are set forth without any loss of generality, and without imposing limitations, relating to the claimed invention,

|0013] The present invention addresses problems associated with prior art methods for the stimulation of sandstone formations at high temperatures and the highly corrosive acids typically employed, and provides a ne non-acidic stimulation methods. The methods described herein generally include a three step process consisting of injecting a preflush brine, followed by injecting a non-acidic stimulation fluid, and finally injecting an overflusli brine. Generally, the non-acidic stimulation fluid reacts with the sandstone formation slowly to enable deeper penetration into the sandstone formation. Additionally, the use of a non- acidic stimulation fluid does not result in the formation of precipitates during reaction.

|0014] As used herein, "sandstone" refers to any formation primarily composed of quartz sand and various forms of feldspar and clays. The grains of sandstone rock are traditionally sand-sized.

[0015] As used herein, "preflush" refers to a fluid pumped into the wellbore ahead of the main stimulation treatment fluids to displace potassium, sodium, and calcium ions in order to minimize the possibility adverse reactions with the treating fluids (e.g. clogging the pores of the foundation).

[0016] As used here, "overf!ush" refers to a fluid, pumped into the wellbore after the stimulation treatment is complete. The overflusli fluid helps to push the main treatment fluid deeper into the sandstone formation and away from the near-wellbore formation to prevent precipitation of reaction products as the treatment fluids are flowed back.

[0017] As used herein, "brine" refers to an aqueous solution containing dissolved inorganic salts that is solid-free.

[0018] In one aspect, a method for injecting a non-acidic stimulation fluid into a high temperature sandstone formation is provided. In one embodiment, the method consists of three steps - injection a preflush brine solution, followed by injecting a non-acidic stimulation fluid, and then injecting an overflusli brine solution.

[0019] In one embodiment of this invention, the preflush brine solution can be selected from a group of halide-containing brines. In one embodiment, the preflush brine can be aqueous ammonium chloride in a concentration range of between 5 to 10% by weight, alternatively between 5-8% by weight. In other embodiments, the preflush brine can be ppoottaassssiiuumm cchhlloorriiddee.. IInn aa pprreeffeerrrreedd eemmbbooddiimmeenntt,, ccoonncceennttrraattiioonn ooff ppoottaassssiiuumm cchhlloorriiddee w wiillll bbee iinn aa rraannggee ooff bbeettwweeeenn 33 aanndd 88 %% bbyy wweeiigghhtt,, mmoorree pprreeffeerraabbllyy 44--66%% bbyy wweeiigghhtt..

[[00002200]] IInn oonnee eemmbbooddiimmeenntt ooff tthhiiss iinnvveennttiioonn,, tthhee nnoonn--aacciiddiicc ssttiimmuullaattiioonn fl fluuiidd ccaann bbee a a ssooddiiuumm hhyyddrrooxxiiddee ssoolluuttiioonn.. IInn cceerrttaaiinn eemmbbooddiimmeennttss,, tthhee ccoonncceennttrraattiioonn ooff tthhee ssooddiiuumm hhyyddrrooxxiiddee ssoolluuttiioonn ccaann bbee iinn aa rraannggee ooff bbeettwweeeenn 55 ttoo 2288%% bbyy wweeiigghhtt,, pprreeffeerraabbllyy ffrroomm 55--1155%% bbyy wweeiigghhtt,, mmoorree pprreeffeerraabbllyy 55--88%% bbyy wweeiigghhtt.. TThhee ssooddiiuumm hhyyddrrooxxiiddee ssoolluuttiioonn iiss ggeenneerraallllyy iinnjjeecctteedd iinnttoo tthhee hhiigghh tteemmppeerraattuurree ssaannddssttoonnee ffoorrmmaattiioonn ddiirreeccttllyy aafftteerr tthhee iinnjjeeccttiioonn ooff tthhee pprreeflfluusshh bbrriinnee,, aanndd bbeeffoorree tthhee iinnjjeeccttiioonn ooff tthhee oovveerrffiiuusshh bbrriinnee.. IInn cceerrttaaiinn eemmbbooddiimmeennttss,, tthhee ssooddiiuumm hhyyddrrooxxiiddee ssoolluuttiioonn iiss aalllloowweedd ttoo rreeaacctt wwiitthh tthhee ssaannddssttoonnee ffoorrmmaattiioonn foforr mmoorree tthhaann tthhrreeee hhoouurrss.. IInn aannootthheerr eemmbbooddiimmeenntt,, tthhee nnoonn--aacciiddiicc ssttiimmuullaattiioonn flfluuiidd ccaann bbee aa ppoottaassssiiuumm hhyyddrrooxxiiddee ssoolluuttiioonn.. IInn cceerrttaaiinn eemmbbooddiimmeennttss,, tthhee ccoonncceennttrraattiioonn ooff tthhee ppoottaassssiiuumm hhyyddrrooxxiiddee ssoolluuttiioonn ccaann bbee iinn aa rraannggee ooff bbeettwweeeenn 55 ttoo 2288%% bb wweeiigghhtt,, pprreeffeerraabbllyy 55--1155%% bb wweeiigghhtt,, mmoorree pprreefeferraabbllyy 55--88%% bbyy wweeiigghhtt.. TThhee ppoottaassssiiuumm hhyyddrrooxxiiddee ssoolluuttiioonn iiss ggeenneerraallllyy iinnjjeecctteedd iinnttoo tthhee hhiigghh tteemmppeerraattuurree ssaannddssttoonnee ffoorrmmaattiioonn ddiirreeccttllyy aafftteerr tthhee iinnjjeeccttiioonn ooff tthhee pprreefflluusshh bbrriinnee,, aanndd bbeeffoorree tthhee iinnjjeeccttiioonn ooff tthhee oovveerrffiiuusshh bbrriinnee.. IInn cceerrttaaiinn eemmbbooddiimmeennttss,, tthhee ppoottaassssiiuumm hhyyddrrooxxiiddee ssoolluuttiioonn iiss aalllloowweedd ttoo rreeaacctt w wiitthh tthhee ssaannddssttoonnee ffoorrmmaattiioonn ffoorr mmoorree tthhaann tthhrreeee hhoouurrss..

[[00002211 ]] IInn oonnee eemmbbooddiimmeenntt ooff tthhiiss iinnvveennttiioonn,, tthhee oovveerrffiiuusshh bbrriinnee ssoolluuttiioonn ccaann bbee sseelleecctteedd ffrroomm a a ggrroouupp ooff lliiaalliiddee--ccoonnttaaiinniinngg bbrriinneess.. IInn.. oonnee eemmbbooddiimmeenntt,, tthhee oovveerrffiiuusshh bbrriinnee ccaann bbee aaqquueeoouuss aammmmoonniiuumm cchhlloorriiddee iinn aa ccoonncceennttrraattiioonn rraannggee ooff bbeettwweeeenn 55 ttoo 1100%% bbyy w w^reeiigghhtt,, aalltteernrnaattiivveellyy bbeettwweeeenn 55--77%%,, 77--99%% oorr 99--1100%% bbyy wweeiigghhtt..

[[00002222]] IInn cceerrttaaiinn eemmbbooddiimmeennttss ooff tthhiiss iinnvveennttiioonn,, tthhee nnoonn--aacciiddiicc ssttiimmuullaattiioonn fflluuiidd iiss pprreehheeaatteedd ttoo aa tteemmppeerraattuurree iinn aa rraannggee ooff bbeettwweeeenn 2200 ttoo 7700°°CC bbeeffoorree iinnjjeeccttiioonn.. IInn cceerrttaaiinn eemmbbooddiimmeennttss,, tthhee tteemmppeerraattuurree rraannggee ooff tthhee nnoonn--aacciiddiicc ssttiimmuullaattiioonn fflluuiidd ccaann bbee iinn aa rraannggee bbeettwweeeenn 5500 ttoo 7700°°CC,, aass tthhee hhiigghheerr tteemmppeerraattuurree eennhhaanncceess tthhee ssttiimmuullaattiioonn eeffffiicciieennccyy ooff tthhee ssooddiiuumm hhyyddrrooxxiiddee ssoolluuttiioonn bbyy eennaabblliinngg aa sslloowweerr rreeaaccttiioonn ttiimmee wwiitthh aanndd ddeeeeppeerr ppeenneettrraattiioonn iinnttoo tthhee ffoorrmmaattiioonn rroocckk..

[0024] The examples below are provided to show a certain exemplary non-acidic sandstone stimulation fluid, as described herein, and its solubility in sandstone formation at differing concentrations and temperatures. A sodium hydroxide solution was allowed to react with sandstone formation at varying temperatures and concentrations for three hours. As shown in Table 1 , a 5% by weight sodium hydroxide solution, was preheated, to temperatures of 23°C and 49°C, and allowed to react with the sandstone formation for 3 hours. The solubility of the sodium hydroxide solution in the formation rock at these temperatures was 2.4 % by weight and 3.2% by weight, respectively. In another test, a 15% by weight sodium hydroxide solution, preheated to 70°C, was allowed to react with the sandstone formation and its solubility in the sandstone formation was 4.55% by weight. The examples show a clear correlation that increasing the temperature and concentration of the sodium hydroxide solution increases the sodium hydroxide solutions' permeability in the sandstone formation.

Table 1

[0025] Although the present invention has been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereupon without departing from the principle and scope of the invention. Accordingly, the scope of the present invention should be determined by the following claims and their appropriate legal equivalents.

|0026] The singular forms "a", "an" and "the" include plural referents, unless the context clearly dictates otherwise.

[0027] Optional or optionally m ans that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0028] Ranges may be expressed herein as from one particular value, and/or to another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said, range.

[0029] Throughout this application, where patents or publications are referenced, the disclosures of these references m their entireties are intended to be incorporated by reference into this application, in order to more fully describe the state of the art to which the invention pertains, except when these reference contradict the statements made herein.

Claims

CLAIMS That which is claimed is:

1. A non-acidic method for the stimulation of sandstone formations, the method comprising the steps of

injecting a preflush brine solution into the wellbore such that the brine solution displaces potassium, sodium and calcium ions in the sandstone formation;

injecting a basic solution into the wellbore; and

injecting an overflush brine solution into the wellbore.

2. The method of claim 1 wherein the preflush brine is selected from a group of halide- containing brines.

3. The method of any of claims 1 and 2, wherein the preflush brine is aqueous ammonium chloride in a concentration range of between 5 to 10% by weight.

4. The method of any of claims 1-3, wherem the aqueous ammonium chloride brine of claim 3, wherein the concentration range is between 5-8% by weight.

5. The method of any of claims 1-4, wherein the aqueous ammonium chloride brine of claim 3, wherein the concentration range is between 8-9% by weight.

6. The method of any of claims 1 -5, wherein the aqueous ammonium chloride brine of claim 3, wherein the concentration range is between 9-10% by weight.

7. The method of any of claims 1-6, wherein the basic solution is a sodium hydroxide solution.

8. The sodium hydroxide of claim 7, wherein the concentration of the sodium hydroxide solution is in a range of between 5 and 28 % by weight.

9. The sodium hydroxide of claim 7, wherein the concentration of the sodium hydroxide is in a range of between 5-8% by weight.

10. The sodium hydroxide of claim 7, wherein the concentration of the sodium hy droxide is in a range between 5-15% by weight.

1 1. The sodium hydroxide solution of claim 7, wherein the concentration of the sodium hydroxide is in a range between 20 to 70°C, prior to injection.

12. The method of any of claims 1-1 1, wherein the overtlush brine is selected from a group of halide-containmg brines.

13. The method of any of claims 1-1 1, wherein the overflush brine is aqueous ammonium chloride in a concentration range of between 5 to 10% by weight.

14. The aqueous ammonium chloride brine of claim 13, wherein the concentration range is between 5-7% by weig t.

15. The aqueous ammonium chloride brine of claim 13, wherem the concentration range is between 7-9% by weight.

16. The aqueous ammonium chloride brine of claim 13, wherem the concentration range is between 9- 10% by weight.