Patent Application
20240166934
Oil and gas operations involve the circulation of drilling fluid throughout the drilling operation. Drilling fluid, also referred to as drilling mud, may include a water, oil, or synthetic base fluid. The choice for using a specific type of base fluid depends on the field conditions and operation requirements at a particular drilling site.
Water-based drilling mud is often a preferred choice, as the preparation cost is low compared to oil-based and synthetic-based mud systems. Moreover, water-based drilling mud is preferred because of its environmentally benign nature. Groundwater is often the source for a water-based mud formulation. In contrast, the use of recycled high salinity wastewater for a water-based mud formulation is not common for various reasons, including compatibility issues with chemical additives, corrosion of downhole equipment, issues during cementing due to impurity, and formation damage issues.
Zero Liquid Discharge (ZLD) is a treatment process for removing liquid waste from a system. The purpose of ZLD is to reduce wastewater economically and produce clean water that is suitable for reuse. Disposal of waste discharge from ZLD-produced water desalination plants remains an issue due to environmental concerns if the water may be discharged on land or water bodies. A produced water desalination plant employs a pre-treatment system to lower residual oil and dissolved H2S content to less than 10 parts per million (ppm) in produced water. The pre-treated produced water is then processed using an evaporation based “dynamic vapor recovery” technology to desalinate the produced water.
The discharge obtained from ZLD-produced water desalination may be used for different upstream applications, such as injection water for reservoir re-injection in water flooding, makeup water for improved oil recovery and/or enhanced oil recovery (IOR/EOR) processes, desired low salinity water for fracking operations, wash water for crude oil desalting, and irrigation.
The water recovery efficiency in a typical ZLD produced water desalination system is approximately 80-90%; however, the system generates up to 10-20% volume of concentrated brine enriched with salts as the waste discharge. The discharge of these concentrated waste brines back into the sea can affect the organisms in the discharge area. Discharge on land leaves salt residue deposition after evaporation. Due to the high saline concentration of the discharge water, there are currently limited options for recycling of the discharge water.
This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
In one aspect, embodiments disclosed herein relate to a wastewater-based drilling fluid comprising a high salinity wastewater discharge occupying from about 40% to about 60% by volume of the wastewater-based drilling fluid, calcium carbonate as a bridging agent, and barite as a weighting agent. The wastewater-based drilling fluid possesses a set of rheological properties and filtration control properties characteristic of a water-based drilling fluid.
In another aspect, the high salinity wastewater discharge comprises 100,000 parts per million (ppm) to 200,000 ppm of sodium and 100,000 ppm to 200,000 ppm of chloride.
In another aspect, the high salinity wastewater discharge comprises 1,000 ppm to 3,000 ppm of sulfate, 1,000 ppm to 2,000 ppm of bicarbonate, 3,000 ppm to 6,000 ppm of potassium, 25,000 ppm to 50,000 ppm of calcium, and 3,000 ppm to 6,000 ppm of magnesium.
In another aspect, calcium carbonate is present in an amount ranging from 12% (w/v) to 16% (w/v).
In another aspect, barite is present in an amount ranging from 15% (w/v) to 25% (w/v).
In yet another aspect, the wastewater-based drilling fluid comprises bentonite in an amount ranging from 2% (w/v) to 4% (w/v).
In another aspect, the high salinity wastewater discharge is a zero liquid discharge (ZLD) wastewater discharge.
Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.
In one aspect, embodiments disclosed herein relate to the use of high salinity wastewater discharge from Zero Liquid Discharge (ZLD)-produced water desalination plants for drilling fluid applications. Conventionally, tap water or fresh groundwater are used to produce drilling fluid formulations. The formulation according to embodiments of this disclosure uses salt ridden wastewater discharged from ZLD desalination plants as a base fluid to formulate water mud formulation. A ZLD desalination plant, or ZLD produced water management system, uses dynamic vapor recovery technology to generate desired quality low salinity water from produced water for different upstream application. A waste stream is generated following removal of salt from the produced water. The wastewater from the waste stream may be collected and used to formulate the water-based mud described herein. The formulation described herein enables the recycling of ZLD wastewater discharge to avoid disposal concerns for the environment. Additionally, significant volumes of fresh groundwater may be saved with the recycling of the wastewater discharge.
Conventional additives in water-based mud were evaluated for use in wastewater-based mud. Specifically, conventional additives were screened in tap water alone as well as a tap water and ZLD wastewater discharge mixture. The two solutions were compared in order to achieve properties suitable for drilling fluid applications. Experiments were conducted that exemplify the invention. The results are presented in
To achieve a drilling fluid formulation useful for drilling fluid applications, the rheological properties and filtration control properties of the wastewater-based drilling fluid formulation need to be similar to those in conventional water-based drilling fluid formulations. Typically, drilling mud rheology is measured continuously during drilling at the rig site. The drilling mud rheology is adjusted with additives and/or dilution to meet drilling operation requirements. The rheology of a fluid may be characterized in terms of plastic viscosity (PV) and yield point (YP) parameters. The YP and PV are parameters from the Bingham plastic (BP) rheology model. PV is the resistance to flow caused by mechanical friction. The PV represents the viscosity of a fluid when extrapolated to infinite shear rate and is expressed in units of centipoise (cP). The PV indicates the type and concentration of the solids in the fluid. The PV parameter is affected by the concentration of solids in the drilling fluid, sizes and shapes of solids, and viscosity of the fluid phase. A low PV is desired.
The YP parameter is determined by extrapolating the BP model to a shear rate of zero, which represents the stress required to move the fluid. The YP is expressed in units of pounds per 100 square feet (lb/100 ft2). The YP is used as an indicator of the ability of drilling fluids to suspend solids and remove them from the wellbore, also known as carrying capacity or hole cleaning ability.
For the purposes of this disclosure, both PV and YP were calculated using 300 revolutions per minute (rpm) and 600 rpm shear rate readings on a standard oilfield viscometer as follows:
PV=(600 rpm reading)−(300 rpm reading) (1)
YP=(300 rpm reading)−PV. (2)
Additionally, the filtration control properties of a drilling fluid are significant to its effectiveness, particularly when drilling through permeable formations in which the hydrostatic pressure exceeds the formation pressure. A drilling fluid needs to quickly form a filter cake, which effectively minimizes fluid loss. In addition, the drilling fluid must be thin and erodible enough to allow product to flow into the wellbore during production. Filtration control materials, such as starch-based biopolymers, reduce the amount of fluid that will be lost from the drilling fluid into a subsurface formation.
Some chemical additives typically used in water-based mud may be incompatible with ZLD wastewater discharge due to its high salinity. The table in
Each of the formulations was produced with amounts of caustic soda (sodium hydroxide (NaOH)), XC polymer (Xanthan gum biopolymer), a starch, and Rev Dust as initial additives, as listed in
Properties analyzed included density (a filtration control property), gel strength, PV, YP, high temperature high pressure (HTHP) spurt loss, and HTHP fluid loss. HTHP spurt loss is the amount of fluid lost in the first part of the experiments, such as the first 30 seconds of the experiment. Spurt loss is the instantaneous volume of liquid that passes through a filter medium prior to deposition of a filter cake. HTHP fluid loss is the amount of fluid lost during the entire experiment time, such as 30 minutes. Each of these properties was analyzed before (BHR) and after (AHR) hot rolling to assess characteristics of the additives before and after exposure to high temperature and high pressure. Gel strength of a drilling fluid is defined as the shear stress measured at a low shear rate after a mud has set for a period of time, typically ten seconds and ten minutes.
Additional additives were evaluated for compatibility in additional experiments. Specifically, amounts of calcium carbonate fine, calcium carbonate medium, and barite were added to the formulation. The table in
Parameters analyzed included density, gel strength, PV, YP, HTHP spurt loss, and HTHP fluid loss. Each of these parameters was analyzed before (BHR) and after (AHR) hot rolling. The rheological properties analyzed were all within ranges considered acceptable for an effective drilling fluid formulation. The filtration control property for the formulation with the additional additives was determined to be acceptable even for the formulation that was hot rolled for 16 h at 500 psi and 212° F., as indicated by the YP, gel strength, and HPHT fluid loss values. YP is the primary indicator of the rheological property of the drilling mud formulation. The recommended YP depends on several factors, such as formation type, mud type, and hole section. A YP value in the range of 10 to 40 is considered acceptable. Ideally, the filtration control properties, HTHP spurt loss and HTHP fluid loss, are as low as possible. A range of 5 ml to 25 ml of filtration loss is considered acceptable.
Bentonite is a common additive used in drilling fluid to provide viscosity along with XC polymer. Hence, determining properties of bentonite that make it compatible with ZLD wastewater discharge is significant in producing a robust drilling fluid formulation. The table in
As shown in
Furthermore, a formulation with the addition of sodium chloride (NaCl), was analyzed. As the ZLD wastewater discharge was known to be saturated with salts, it was expected that the addition of NaCl would deteriorate the properties of the mud formulation. As shown in the table of
The drilling fluid formulation using 50% tap water, 50% ZLD wastewater discharge, and the additives presented in
The drilling fluid formulation described herein uses high salt concentrated waste reject streams obtained from ZLD wastewater discharge to formulate water-based mud formulations for drilling applications. Such applicability of wastewater streams for potential reuse in drilling applications avoids the waste disposal to the environment and contributes to environmental sustainability.
Unless defined otherwise, all technical and scientific terms used have the same meaning as commonly understood by one of ordinary skill in the art to which these systems, apparatuses, methods, processes, and compositions belong.
The singular forms “a,” “an,” and “the” include plural referents, unless the context clearly dictates otherwise.
As used here and in the appended claims, the words “comprise,” “has,” and “include” and all grammatical variations thereof are each intended to have an open, non-limiting meaning that does not exclude additional elements or steps.
“Optionally” means 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.
When the word “approximately” or “about” are used, this term may mean that there can be a variance in value of up to ±10%, of up to 5%, of up to 2%, of up to 1%, of up to 0.5%, of up to 0.1%, or up to 0.01%.
Ranges may be expressed as from about one particular value to about another particular value, inclusive. When such a range is expressed, it is to be understood that another embodiment is from the one particular value to the other particular value, along with all particular values and combinations thereof within the range.
While the disclosure includes a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the present disclosure. Accordingly, the scope should be limited only by the attached claims.
