REAL TIME DOWNHOLE WATER CHEMISTRY AND USES

Abstract

Method of monitoring produced water at each perforation or entry point by real time ion sensor deployed downhole to measure the content of water soluble ions. Methods of determining and differentiating nature of water breakthrough in oil production; such as between cycled injection water through a void space conduit, matrix swept injection water and formation water, especially as relates to offshore oil production. Real time ion sensors are deployed and when compared with known standards are used to monitor and remediate water breakthrough, prevent scale deposition, and the like.

Claims

1) A method of optimizing hydrocarbon production and minimizing produced water production; said method comprising: a) deploying a tool comprising one or more ion sensitive sensor(s) downhole in a hydrocarbon well in a formation; b) measuring a concentration of at least two ions in water at an inflow perforation in said well using said one or more ion sensitive sensor(s), said at least two ions selected from calcium, sodium, chloride, magnesium, strontium, sulfur, iron and boron; c) comparing said measured concentrations against known concentrations of said at least two ions in one or more of i) natural formation water from said formation, ii) water injected into said formation, and iii) seawater above said formation if said well is an offshore well; d) determining a contribution of one or more of i), ii) and iii) to produced water based on said comparison; and e) applying mitigation remedies to reduce said contribution from i), ii) and/or iii), thereby optimizing hydrocarbon production and minimizing produced water production.

2) The method of claim 1, wherein measuring step b is repeated at each perforation or at each perforation cluster.

3) The method of claim 1, wherein perforations are identified by a change in temperature or a change in flow rate, and said tool comprises a temperature sensor and/or a flow sensor.

4) The method of claim 1, wherein said measuring step b is continuous and said measuring occurs before, at, and after each perforation or perforation cluster.

5) The method of claim 1, wherein said measuring includes determining calcium, sodium and chloride, and Na.sup.+/Cl.sup.− and Ca.sup.2+/Cl.sup.− ratios.

6) The method of claim 1, wherein said tool also includes a pH meter, and pH is measured and used in said comparing step c; or wherein said tool also includes a thermometer, and temperature is measured and used in said comparing step c.

7) The method of claim 1, wherein formation water is sampled during drilling to obtain said known concentrations and/or wherein injection water is sampled before injection to obtain said known concentrations, and/or wherein seawater is sampled to obtain said known concentrations.

8) The method of claim 1, wherein said at least two ions present in hydrocarbons obtained from said reservoir are subtracted from measurements obtained in measuring step b; or wherein hydrocarbons are sampled from said reservoir and said at least two ions therein are determined and are subtracted from measurements obtained in measuring step b.

9) The method of claim 1, wherein contributions of one or more of i) ii) and ii) are determined by mass analysis.

10) The method of claim 1, wherein said one or more ion sensor(s) are selected from an ion selective field effect transistor, an ion selective electrode, an ion selective electrode with a solid state electrode, an optical sensor, and an electrochemical sensor.

11) A method of monitoring produced water production; said method comprising: a) deploying a tool comprising ion sensitive sensors comprising a calcium sensitive sensor, a sodium sensitive sensor and a chloride sensitive sensor, plus a temperature sensor plus a flow rate sensor downhole in a hydrocarbon well in a formation; and b) drawing said tool upwell and continuously measuring the following: i) a concentration of at least calcium, sodium, and chloride ions; ii) a temperature; iii) a rate of flow; c) determining inflow positions along said well by a change in temperature and/or rate of flow; d) obtaining Na.sup.+/Cl.sup.− and Ca.sup.2+/Cl.sup.− ratios at each inflow positions; e) comparing obtained Na.sup.+/Cl.sup.− and Ca.sup.2+/Cl.sup.− ratios and known Na.sup.+/Cl.sup.− and Ca.sup.2+/Cl.sup.− from one or more of i) natural formation water from said formation, ii) water injected into said formation, and iii) seawater above said formation (if said well is an offshore well); f) determining a contribution of one or more of i), ii) and iii) to produced water based on said comparison at each inflow position.

12) The method of claim 11, wherein said tool also includes a pH meter, and pH is measured and used in said comparing step.

13) The method of claim 11, wherein formation water is sampled during drilling to obtain said known concentrations, or wherein injection water is sampled before injection to obtain said known concentrations, or wherein seawater is sampled to obtain said known concentrations.

14) The method of claim 11, wherein contributions of one or more of i) ii) and ii) are determined by mass analysis.

15) The method of claim 11, wherein said ion sensitive sensors are selected from an ion selective field effect transistor, an ion selective electrode, an ion selective electrode with a solid state electrode, an optical sensor, and an electrochemical sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1. Ions in surface seawater.

[0046] FIGS. 2A, 2B and 2C. Drawing a sensor tool upwell in and taking continuous or near continuous measurements as the tool traverses up the well.

[0047] FIG. 3. A simplified schematic of an ion sensor well tool.

DETAILED DESCRIPTION

[0048] The present invention is exemplified with respect to downhole detection of Ca.sup.2+ Na.sup.+, and Cl.sup.−. However, this is exemplary only, and the invention can be broadly applied to many different ions and/or analytes for which rugged sensors are available. The following examples are intended to be illustrative only, and not unduly limit the scope of the appended claims.

[0049] Tools that may be used in the invention include the environmental capture sonde (ECS) by SCHLUMBERGER®—a short, easy to use tool that measures and processes gamma ray spectra, and for accurately defining clay content, mineralogy, and matrix properties. ECS determines relative elemental yields by measuring the gamma rays produced when neutrons bombard the formation and lose energy as they are scattered, primarily by hydrogen. The primary formation elements measured by the ECS in open and cased holes are the most commonly occurring elements: Si, Fe.sup.2+/3+, Ca.sup.2+, S, Ti.sup.3+, Gd.sup.3+, Cl.sup.−, Ba.sup.2+ and H.sup.+.

[0050] Other measurements that may be taken simultaneously include temperature, pressure, density, capacitance, and spinner (flow rate), and the like.

[0051] Unlike surface water chemistry, downhole water chemistry measurement will not have the direct water sample available. In this case, an indirect method-like element spectroscopy, optical analyzer, electrochemical methods could also be used.

[0052] Since the samples being analyzed are mixed oil, gas and water samples, the tool selected will need to be able to withstand such conditions and be able to track water born ions even when crude oil is present. Thus, proof of concept work will likely require comparison against produced fluids that are samples, separated and analyzed in bench top experiments. Even when there are differences between the two types of analysis, collection of sufficient downhole and bench top data will allow us to provide the needed correction factors.

[0053] For example, crude oil also contains sulfur, nitrogen, and oxygen in small quantities. Metals present in the crude oil are mostly Ni(II) and V(II) porphyrins and non-porphyrins. Other metal ions reported form crude oils, include copper, lead, iron, magnesium, sodium, molybdenum, zinc, cadmium, titanium, manganese, chromium, cobalt, antimony, uranium, aluminum, tin, barium, gallium, silver, and arsenic. Any of these could contribute to data if these elements were detected, but predetermination of their amounts in a play would allow subtraction from the downhole data.

[0054] FIG. 1 shows the top 11 ions in seawater, any one of which can be measured herein. Preferably, non-conservative ions such as calcium, strontium and magnesium are measured so that one can tell the approximate depth of the seawater.

[0055] FIG. 2A shows an ion sensor 209 being deployed downhole in production tubing 201, with a number of perforations or perforation clusters 203, 205 and 207. As the tool 209 is drawn uphole in FIGS. 2B and 2C, via e.g., wireline 211, it collects data, which is typically sent to a computer 213 on the surface. Inflow typically increases at each perforation (see arrows in 2B and 2C) and such data is particularly useful.

[0056] The tool itself 300 is shown in simplified schematic in FIG. 3. Tool 300 has an exterior housing 308 with one or more inlets 310 and outlets 309. As fluid enters the tool 300 (see dotted line for fluid flow) it encounters a variety of sensors, including flow sensor 301 and temperature sensor 303, which could also be on the surface of the housing 308, but here shown inside for protection. Also seen are ion sensors 304, 305, and 306, as well as processor 307 for processing and recording data. Data is typically sent to the surface via wireline 311 or it could also be sent wirelessly if such components are included therein. Electrical connections are omitted herein for simplicity.

[0057] Using the devices and methods described herein, it becomes possible to quantify either total water or the proportion of produced natural formation water versus flowback versus seawater from each perforation at any given condition—such as steady state and stable flowing, transient condition, cross flow or complete shut-in/no flow, etc. Armed with this information, the operator can take appropriate steps to remediate the excess production of various waters and thus optimize the economics of hydrocarbon production.

[0058] This technology should be able to calculate ion concentration of water in a multiphase situation such as water, oil, and gas, and should be applicable in any type of well trajectory such as vertical, slanted, highly deviated, horizontal lateral.

[0059] Once the water chemistry is fully analyzed for wells in a field, it will add tremendous value towards tracking the flood front and evaluate the sweep efficiency of the flood. The water chemistry should also indicate section of the wellbore susceptible to scaling, and therefore help in prevention or scale removal well intervention.

[0060] The sensors and downhole analyzer instrument can be added to a profile logging tool or as a separate individual drift run. This could be run as usual with wireline/pipe conveyed logging/tractor. However, a preferred option may be to attach it with a production logging tool (PLT).

[0061] When in contact with water downhole, the tool would be estimating the ionic concentration of the water in real-time or near real-time and transmit that data to surface with other data like pressure, temperature, capacitance, flow rates, etc. The engineer will then be able to detect the types of water contributed by each perforation/sleeve/zone and adjust as needed.

[0062] Any method of calculating the contributions of the various sources to the produced water may be used. For example, isotope-based statistical mixing models are commonly used by ecologists to estimate food source proportions in complex ecosystems but can be also used for a wide range of applications. Herein, a mixing model known as SIAR could be used to estimate water source proportions (see e.g., Kruse, 2014).

[0063] SIAR (Stable Isotope Analysis in R) is an open source software package that runs in the free statistical computing environment “R” (r-project.org/) (Parnell, 2010). The model uses Markov Chain Monte Carlo (MCMC) methods to produce simulations of possible source proportions consistent with the data using a Dirichlet prior distribution. The resulting posterior probability density distributions of the feasible source proportions allow direct identification of the most likely solution, and upper and lower credibility intervals describe the possible range of source proportions. MixSIR is fundamentally very similar (Moore & Semmens, 2008).

[0064] IsoSource (Phillips & Gregg, 2003) is another model commonly used to evaluate these such problems, providing a suite of possible or feasible solutions. It does so by iteratively evaluating all possible combinations of each source contribution (0-100%) in small increments (e.g., 1%). Combinations that sum to the observed isotopic composition of the mixture, within a small tolerance (e.g., 0.1% o), are considered as feasible solutions, from which the frequency and range of potential source contributions is determined.

[0065] The invention includes any one or more of the following embodiment(s) in any combination(s) thereof, but each possible combination is not separately listed in the interests of brevity:

[0066] A method of optimizing hydrocarbon production and minimizing produced water production; said method comprising:

[0067] deploying a tool comprising one or more ion sensitive sensor(s) downhole in a hydrocarbon well in a formation;

[0068] measuring a concentration of at least two ions in water at an inflow perforation in said well using said one or more ion sensitive sensor(s), said at least two ions selected from calcium, sodium, chloride, magnesium, strontium, sulfur, iron and boron;

[0069] comparing said measured concentrations against known concentrations of said at least two ions in i) natural formation water from said formation, ii) water injected into said formation, and iii) seawater above said formation if said well is an offshore well;

[0070] determining a contribution of i), ii) and iii) to produced water based on said comparison; and

[0071] applying mitigation remedies to reduce said contribution from i, ii and/or iii), thereby optimizing hydrocarbon production and minimizing produced water production.

[0072] A method of monitoring produced water production; said method comprising:

[0073] deploying a tool comprising ion sensitive sensors comprising a calcium sensitive sensor, a sodium sensitive sensor and a chloride sensitive sensor, plus a temperature sensor plus a flow rate sensor downhole in a hydrocarbon well in a formation; and

[0074] drawing said tool upwell and continuously measuring the following:

[0075] a concentration of at least calcium, sodium, and chloride ions;

[0076] a temperature;

[0077] a rate of flow;

[0078] determining inflow positions along said well by a change in temperature and/or rate of flow;

[0079] obtaining Na.sup.+/Cl.sup.− and Ca.sup.2+/Cl.sup.− ratios at each inflow position;

[0080] comparing obtained Na.sup.+/Cl.sup.− and Ca.sup.2+/Cl.sup.− ratios and known Na.sup.+/Cl.sup.− and Ca.sup.2+/Cl.sup.− from i) natural formation water from said formation, ii) water injected into said formation, and iii) seawater above said formation (if said well is an offshore well);

[0081] determining a contribution of i), ii) and iii) to produced water based on said comparison at each inflow position.

[0082] Any method herein described, wherein measuring step is repeated at each perforation or at each perforation cluster or other opening in the well that allows inflow of fluids.

[0083] Any method herein described, wherein perforations are identified by a change in temperature or a change in flow rate, and said tool comprises a temperature sensor and/or a flow sensor.

[0084] Any method herein described, wherein said measuring step is continuous and said measuring occurs before, at, and after each perforation.

[0085] Any method herein described, wherein said measuring includes determining calcium, sodium and chloride, and Na.sup.+/Cl.sup.− and Ca.sup.2+/Cl.sup.− ratios.

[0086] Any method herein described, wherein said tool also includes a pH meter, and pH is measured and used in said comparing step.

[0087] Any method herein described, wherein said tool also includes a thermometer, and temperature is measured and used in said comparing step.

[0088] Any method herein described, wherein formation water is sampled during drilling to obtain said known concentrations, and/or wherein injection water is sampled before injection to obtain said known concentrations, and/or wherein seawater is sampled at any time to obtain said known concentrations.

[0089] Any method herein described, wherein said one or more ion sensor(s) are selected from an ion selective field effect transistor, an ion selective electrode, an ion selective electrode with a solid state electrode, an optical sensor, and an electrochemical sensor.

[0090] The following references are each incorporated by reference in their entirety for all purposes:

[0091] U.S. Pat. Nos. 7,373,813 and 8,104,338 Method and apparatus for ion-selective discrimination of fluids downhole.

[0092] U.S. Pat. No. 9,435,192 Downhole electrochemical sensor and method of using same.

[0093] U.S. Pat. No. 9,863,243 Ruggedized downhole tool for real-time measurements and uses thereof.

[0094] U.S. Ser. No. 10/060,250 Downhole systems and methods for water source determination.

[0095] Kruse, M. E. Isotopic fingerprinting of shallow and deep groundwaters in southwestern Ontario and its applications to abandoned well remediation. Thesis (2014) Univ. Westn. Ont.

[0096] Phillips, D. L.; Gregg, J. W. Source partitioning using stable isotopes: coping with too many sources. Oecologia (2003) 136, 261-269.

[0097] Moore J. W.; Semmens B. X. Incorporating uncertainty and prior information into stable isotope mixing models. Ecology Letters (2008) 11, 470-480.

[0098] Parnell A. C., et al., (2010) Source partitioning using stable isotopes: coping with too much variation. PLoS ONE 5, 1-5.