Patent Application
20190263685
The present disclosure relates generally to the field of water treatment, particularly systems and methods using forward osmosis membranes to treat saturated brine in oil and gas production facilities.
Oil and gas production facilities are known to have a variety of water streams present. For every barrel of crude oil produced, about three to ten barrels of water is produced. In the oil and gas industry, water that is drawn from the formation is referred to as “produced water.” Among the variety of water streams present are high salinity brine solutions containing salts such as sodium, calcium or bromides, from such sources as acid treatment units for water softening. In conventional practice, soft water is often used to dilute the high salinity brine solutions. Contaminated wastewater streams are also present resulting from various oil and gas processes and are often used to dilute the high salinity brine solutions. Contaminated wastewater streams can include, for example, pit wastewater (i.e., oily waste waters from various plant operations dumped into a pit) and high fouling and scaling waters (e.g., containing significant amounts of bicarbonates, sulphates, silica, calcium and the like). Most wastewater streams resulting from various processes are sent for disposal. For example, solids removal followed by primary treatment (e.g., dispersed oil removal, suspended solids removal) and secondary treatment (e.g., flotation treatment). In some cases, tertiary treatments (e.g., hardness, dissolved salts) and chemical treatments may also be carried out on the wastewater streams.
There exists a need for more efficient means of using and disposing of both high salinity brine solutions and contaminated wastewater streams in oil and gas production facilities. It would further be desirable to reduce soft water use.
In general, in one aspect, the disclosure relates to processes for forming diluted brine from saturated brine without the addition of soft water in an oil and/or gas treatment facility. The processes include feeding a contaminated water feed containing water and salt contaminants from a source of contaminated water to a feed side of a forward osmosis membrane. The salt contaminants can be cations, anions, carbonate, bicarbonate and combinations thereof. a saturated brine solution is fed to a draw side of the forward osmosis membrane and the forward osmosis membrane allows water to pass from the feed side to the draw side and minimizes the passage of the salt contaminants from the feed side to the draw side. a diluted brine solution having a total dissolved solids concentration lower than a total dissolved solids concentration of the saturated brine solution is removed from the draw side outlet of the forward osmosis membrane. a concentrated contaminated water stream having a total dissolved solids concentration higher than a total dissolved solids concentration of the contaminated water feed is removed from the feed side outlet of the forward osmosis membrane.
In another aspect, the disclosure can generally relate to systems for forming the diluted brine from saturated brine without the addition of soft water in an oil and/or gas treatment facility. The system includes a source of the contaminated water, a source of the saturated brine solution, a forward osmosis membrane having a feed side and a draw side, a feed side inlet and a feed side outlet, a draw side inlet and a draw side outlet, wherein the feed side inlet is connected to the source of contaminated water and the draw side inlet is connected to the source of saturated brine solution, and a diluted brine tank connected to the draw side outlet of the forward osmosis membrane for storing diluted brine solution.
These and other objects, features and advantages of the present invention will become better understood with reference to the following description, appended claims and accompanying drawings. The drawings are not considered limiting of the scope of the appended claims. Reference numerals designate like or corresponding, but not necessarily identical, elements. The drawings illustrate only example embodiments. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Additionally, certain dimensions or positionings may be exaggerated to help visually convey such principles.
Referring to
In embodiments, a process and system are provided for forming diluted brine from saturated brine without the use of direct addition of soft water or contaminated water in an oil and/or gas treatment facility. Referring to
The feed side inlet 12Ai is connected to a source of contaminated water 9. Wastewater stream 10, also referred to as contaminated water feed 10, from a source of contaminated water 9, e.g., wastewater pit or tank, is fed to the feed side inlet 12Ai of the forward osmosis membrane unit 12. In one embodiment, the wastewater stream 10 can be produced water associated with oil and/or gas production. The wastewater stream 10 can contain various contaminants including, but not limited to, cations e.g. sodium, potassium, magnesium and/or calcium, anions e.g. chloride and/or sulfate, carbonate, bicarbonate and combinations thereof.
The draw side inlet 12Bi is connected to the source of saturated brine solution 3. A saturated brine solution 2 is fed from the saturated brine tank 3 to a draw side 12B of the forward osmosis membrane unit 12. In one embodiment, the wastewater stream 10 has a total dissolved solids concentration (TDS) of from 5,000 to 50,000 mg/L and the saturated brine solution 2 has a TDS of 50,000 to 357,000 mg/L.
Water is drawn from the feed side of the membrane 12A to the draw side of the membrane 12B by osmotic driving force. Water from the wastewater stream 10 moves across the forward osmosis membrane, thereby diluting the saturated brine solution 2 and forming a diluted brine solution stream 13. In one embodiment, from 20 to 95%, even from 90 to 95%, of the water in the wastewater stream 10 passes from the feed side 12A to the draw side 12B and is recovered in the diluted brine solution 13. The forward osmosis membrane 12 minimizes the passage of the contaminants, also referred to as salt contaminants, from the feed side 12A to the draw side 12B.
The diluted brine solution stream 13 having a TDS lower than a TDS of the saturated brine solution 2 is formed without the direct addition of soft water 1 or contaminated water. The diluted brine 13 is removed from the draw side outlet of the forward osmosis membrane 12. The diluted brine 13 can be sent to the diluted brine tank 4 and the ion exchange unit 6 to regenerate the resin bed, as in the conventional water management system described above with respect to
A concentrated contaminated water stream 14 having a TDS higher than a TDS of the wastewater stream 10 is removed from the feed side outlet of the forward osmosis membrane 12. In one embodiment, the diluted brine solution 13 has a TDS of from 100,000 to 150,000 mg/L and the concentrated contaminated water stream 14 has a TDS of from 25,000 to 150,000 mg/L. The concentrated contaminated water stream 14 can be treated in a water treatment facility (not shown) connected to the feed side outlet of the forward osmosis membrane 12, or in some cases injected into a subterranean reservoir after moderate treatment. The concentrated contaminated water stream 14 can be treated in the water treatment facility using an evaporator crystallizer, a microfiltration unit, and/or an ultrafiltration unit (not shown).
Referring to
Referring to
Referring to
A process using system 100 shown in
A membrane coupon was placed in a forward osmosis membrane module with connections for feed water inlet and outlet on one side and draw water inlet and outlet on the other side. The produced water (pit wastewater; stream 10 from facility 9 in
The flow rates and TDS of the streams 2, 5, 7, 10, and 14 are listed in Table 1. The components detected in the streams 2, 13, 10 and 14 are listed in Table 2.
As a result of the forward osmosis membrane treatment, a sample of the fresh brine stream 5 was visually clear and clean.
A process using system 200 shown in
A membrane coupon was placed in a forward osmosis membrane module with connections for feed water inlet and outlet on one side and draw water inlet and outlet on the other side. The produced water containing oily sludge (stream 10 from facility 9 in
The flow rates and TDS of the streams 2, 5, 7, 10, and 14 are listed in Table 3. The components detected in the streams 10, 16, 7 and 15 are listed in Table 4.
As a result of the forward osmosis membrane treatment, a sample of the final diluted waste brine 15 obtained from the lab experiments was clear in color.
A process using system 300 shown in
A produced water stream 17 containing high levels of silica (about 210 mg/l) and bicarbonates (about 1400 mg/l) was fed to the feed side inlet of forward osmosis membrane 12. A saturated brine solution 2 was fed to the draw side inlet of the forward osmosis membrane 12. A diluted brine solution stream 13 was removed from the draw side outlet of the membrane 12. Diluted brine solution stream 13 has greatly reduced levels of silica and bicarbonates, and therefore has a low scaling potential. The diluted brine solution 13 can be fed to an ion exchange softener vessel 24 without concern for scale formation and without the need for any anti-scalant chemicals like stream 19 in
Using the systems and methods of the present disclosure, direct dilution of saturated brine solution using soft or saturated brine solution is avoided. The dilution of the of saturated brine solution is instead accomplished using an FO membrane. That advantageously leads to lowered concentration of potential scalants in the diluted brine.
It should be noted that only the components relevant to the disclosure are shown in the figures, and that many other components normally part of a water treatment system are not shown for simplicity.
For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the present invention. It is noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the,” include plural references unless expressly and unequivocally limited to one referent.
Unless otherwise specified, the recitation of a genus of elements, materials or other components, from which an individual component or mixture of components can be selected, is intended to include all possible sub-generic combinations of the listed components and mixtures thereof. Also, “comprise,” “include” and its variants, are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that may also be useful in the materials, compositions, methods and systems of this invention.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope is defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. All citations referred herein are expressly incorporated herein by reference.
From the above description, those skilled in the art will perceive improvements, changes and modifications, which are intended to be covered by the appended claims.
