SPE伊朗北阿油田钻井废物处理方法.pdf

spe 156152 how to meet “zero discharge” goal in a sensitive n.azadegan field wetland environment? li rong, china univ geosci(beijing), feng yaping, zhou yunzhang, yang deyin, jiang zhi, cnpci(iran), bi guoqiang, riped-langfang copyright 2012, society of petroleum engineers this paper was prepared for presentation at the spe international production and operations conference and exhibition held in doha qatar, 1416 may 2012. this paper was selected for presentation by an spe program committee following review of information contained in an abstract submitted by the author(s). contents of the paper have not been reviewed by the society of petroleum engineers and are subject to correction by the author(s). the material does not necessarily reflect any position of the society of petroleum engineers, its officers, or members. electronic reproduction, distribution, or storage of any part of this paper without the written consent of the society of petroleum engineers is prohibited. permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. the abstract must contain conspicuous acknowledgment of spe copyright. abstract north azadegan field with more than 4,886mmstb reserve to drill 58 wells in less than 3 years, operation area with average about 2.5m water depth, belongs to one of international nature reserve conservation zones faced with a huge environmental challenge. traditionally onshore operations in iran, water based drilling mud and its cuttings have been disposed of directly on the ground in unlined pits, because disposal of drilling wastes poses no serious threat to the environment. however, a zero- discharge goal is required for this sensitive wetland of n.azadegan field. this paper shares an overview of how to achieve a zero discharge goal in a remote, rural, sensitive wetland, accompanied with the below applicable methods:1)cluster well pad design and construction including waste treatment layout; 2)generic waste management stream for minimizing contamination; 3) treatment of drilling cutting waste as pavage for other pads or road construction; 4)reuse of waste water for mixing mud etc. while contractors waste management equipment and personnel daily rates add to the drilling operation cost of the project for higher cost ceiling under buy-back contract, cutting treatment and mud reuse techniques actually reduce total n.azadegan project cost, combined with careful planning, advanced equipment and services. this paper will report the past experiences and lessons of these waste management methods in n.azadegan. in details, the waste treatment and management technologies integrated with well pad construction will be evaluated feasibly and economically. 1.introduction the n.azadegan field is approximately located 80 kilometers west of ahwaz city, in the west-south dezful embayment, parallel to iran-iraq border. operation area with 1.5-3.5m water depth, swamp with limited drilling area, belongs to one of international nature reserve conservation zones, and there is beautiful nature landscape with so many wild animals such as kinds of birds, wild boar, fox etc as figure1 in the field. figure 1- pad construction in sensitive wetland cluster wells in the pad are the only choice for 8 upgraded 2000hp rigs to drill 58 wells, with strict environment protection in the wetland and less well pad of operation areas for more well counts in one cluster pad.1 the key issue for waste management is drilling mud and its cuttings. a lot of chemicals such as cmc, polymer, lubricant etc. are added into the drilling fluid during drilling process to meet the mud properties or engineering requirements. the majority of components are described as non toxic or having a low-toxicity, because a water- based mud with the principal constituents being potassium chloride kcl, bentonite and polymers.for example, bentonite mud was used in 26 ” hole section, salt saturated mud in 12 1/4 ” hole section and kcl polymer in 17- 1/2”,8-1/2” and 6” hole section. different mud density from 71 to137pcf balances formation pressure for good drilling performance and water based mud reduces the risk of waste management for zero discharge in n.azadegan. 2 spe 156152 iran is becoming increasingly strict environment protection, especially for this wetland. moreover, wastes remain the responsibility of company. it is important to assess what future liabilities may be faced and plan a strategy of limiting liability by sound drilling waste management procedures, which is specially designed for the waste produced during drilling operation such as cutting, drilling fluid etc. 2. well pad design and construction based on reservoir study on n.azadegan oilfield, the cluster well pads and main/access roads will be designed by considering suitable elevation due to the local marsh area. the dimension of cluster well pads and main/access roads should be designed base on drilling practice standards and landscape environment protection. this short period of construction and less cost and land are strongly recommended and less damage and pollution on environment are taken into consideration on construction. the advantage of waste management is disposal cutting while drilling, no pollution to well site, less operation square and waste water recycling then minimize the pollution to environment, based on this kind of well pad. according to geology and environmental protection requirement, well pads and main roads layout is designed and illustrated as figure 2. figure 2 well pads and main roads layout there are about 20 pads and 39km roads by four batches construction, and maximize use of dry cutting from onging drilling wells based on 2000hp rig and equipment layout. then 2 to 5 well number in cluster pads is optimized depend on integrated consideration of geology and engineering for total 58 wells. 2.1 well pads layout the well pads shown in following figures 3 is designed to meet the minimal requirement of 2000hp china-made electrical type rig equipment, which has been proved by previous experience in other field practicing and land- saving. sufficient care is focused on the local wind direction, so the designed direction of well pads can be changed in azimuth angle range of 180-270 degree for proper rigs layout to meet hse requirement. and one more cellar is built as back up for borehole accident. figure3-well cluster pad for 2000hp rig technical specification as follow: 1) the waste diposal area is 7515m, which is designed to collect area, filter area and water recycle by 2m height moving dam. 2) the waste water pit is 30202m, and put concrete foundation on the bottom in order to prevent a risk to the soil and to shallow quifers in unlined pit. the pit is built with a concrete slope bottom, with a concrete path for vehicle entry. 3) burning pit is 10101m,and 300m away from wellhead, and 3m wide simple path is set to fix burning line. 4) the specification of septic pit is 10102m, and at least 70m away from wellhead. 2.2 waste management the final objective of waste management is “zero discharge” for wetland. drilling waste includes wasted barite separated by centrifuges, drilling cuttings, waste fluid/water and so on, a corral area is set behind no.1 mud tank to collect the drilling waste, which is treated by an ancillary equipment/facilities and handling system installed in location. the treating process is synchronous with drilling operation, and then the solid after treating transferred to the otherplace for pavage.when drilling in some unforeseeable downhole condition such as salt water cut 12-1/4” section or heavy rain in winter, several emergency tanks are design to collect more mixed mud and waste water. sketch for the disposal unit: figure4- layout of water treatment system in term of gutter drainage design, company considers the influence factor such as rain water, dirty water, spill water mud circulation tanks waste collecting tank auger for transfering waste mud emergency tank waste disposal unit spe 156152 3 etc for collection and separation. it is easy to collect together illustrated as figure 5 and make it suitable for re- use after simple process. figure5- gutter drainage layout technical specification as below: 1) the deposit pit is 1.51.51m, and 30m away from wellhead. 2) location gutter drainage is designed as 2015cm, and make sure it is smooth. the concrete foundation area cover rig base, mud pumps base, mud tanks base, waste management area, generator base, proper gutter should be built in concrete foundation area to guide waste water as fig 6. figure 6- cluster pad concrete foundation layout the concrete foundation for rig base is designed with mesh of ?1225cm, and for mud pumps base, mud tanks base, waste management area, generator base are designed with mesh of ?820cm. 3. generic waste management stream the extreme climate, more than 55in summer and three months rainy season in winter, provides an unpredictable waste disposal environment. fast drilling technology must be used to improve rate of penetration and shorten drilling time pursuant to maximum 120 day well duration for 4000m sigle well, so it is another big challenge for disposal equipment, for example, about 300-400m footage per day in 17-1/2” hole can produce more than one hundred cubic meter cutting. moreover, downhole problems associated with salt water and hydrocarbon overflow make the waste water unexpectedly more. the waste management system will operate in a zero discharge principle, although the nature of the climate and challenging drilling conditions put periodic strain on the containment and treatment system. the equipment is specified to the highest standards to provide maximum flexibility and performance. care will have to be taken to always follow the route of minimization of waste volumes. facilities must always be available to deal with unexpected discharge requirements and react quickly to change condition.3 the main principle is solid-liquid separation, solid and water process should conform to regulations, laws and discharge requirements. the processed solid is for pavage or landfill, and the processed water can directly be used for new mud. although water is mainly used for new mud, evaporation is another method from waste pit. as the water decreases in chloride content it can be discharged to mash after strictly test or allowed to evaporate completely. salt will crystallize out on the slope and can be removed. according to drilling waste management procedures, service contractor will separate, contain and package wastes for removal from site, therefore, loading, transportation, discharge, disposal site maintenance, liability etc will remain the legal responsibility of company but will be managed by service contractor in line with pre agreed practices and targets. 2 4. drilling cutting disposal and re-using on the rig site, cuttings from the shale shakers are transferred into collecting tank for waste fluid & waste cuttings, there are stirring device and pump in the collecting tank. waste fluid from desander, desilter and centrifuge are discharged into an auger, and then transferred to the collecting tank. waste drilling fluid and waste cuttings are mixed together, and then be pumped into the waste disposal unit for further treatment. figure 7-auger conveyor below shakers drilling waste is transferred to the solid/liquid separator by auger conveyor as fig.7, the solid is separated and solidified, which is used for pavage for access road& pad construction. these are segregated from the top section by a partition in the corral storage area. the saline cuttings continue to leach salt water. this is contained and 4 spe 156152 dewatered by collection in the area and recovered using the submersible pumps. the cutting is segregated from sections transferred by auger to the collecting tank for treatment such as gel breaking, then microporous vavuum filter for remove water, drying equipment to dry as much as possible. solid treatment module is showed as fig8. figure8- waste treatment process illustration figure9-dry cutting on the disposal area receive cuttings after shaker are mix in the cutting treatment area with cement or lime and sodium silicate using the fixation equipment.the cuttings are scooped into the bucket and poured into the cylinder. after treatment, treated cuttings are disposed to the disposal area. if excess volume of cement after displacement, adding required chemical to avoid it getting hard, separate liquid phase and then pass through the drying cylinder. cement mixes with cuttings gather from the drilling phase and after treatment dispose for pavage as fig.10 . figure10 pavage for road with cutting a full suite of waste management equipment provides the flexibility to meet the particular environmental requirements of the project with matched levels of technology. there are about 2000m3 waste solids and cuttings for one appraisal well in n.azadegan, transported for pavage of new road and pad, some for landfill. 5. reuse of waste water reuse system combines physical technique and chemical technique together to deal with waste drilling fluid. the disposal system in the wellsite includes the treatment of waste water. liquid separated can be used for mixing mud, and superfluous liquid shall be transferred to mud plant for further harmless treatment. separated waste water is transferred to waste water disposal unit, then discharged or recycle. process chart as figure 11. fig 11 waste treatment process chart separation of the liquid and solids of a mud system occurs easily as the centrifuge removes the larger flocked solids as a moist sludge as figure 12. fig 12 high speed centrifuge for separating waste fluid from desander, desilter and centrifuge is discharged into an auger, and then transferred to the collecting tank as figure 13. fig 13 rectangle collecting tank for waste drilling fluid dewatering is the process of removing the majority of colloidal size solids in excess of used water base drilling muds by the addition of chemicals such as poly aluminum chloride and poly electrolyte to coagulate and flocculate the solids in the mud thus blended chemically enhanced fluid is pumped to centrifuge. thus dewatering system overcomes this limitation by mud flocculation by pretreating chemically to increase the “effective particle size” of the suspended solids. waste mud gel breaking vacuum and micro hole filtering strong oxidizing decompose water reverse osmosis water reuse waste cuttings gel breaking microporo us vacuum filter separated liquid harmless cutting dry cutting spe 156152 5 fig 14 dewatering equipment the overall objective of a dewatering system is to process the drilling waste for reduction of the liquid waste volume, recycle of the liquid portion, facilitate disposal and release solids in an environmentally safe and cost effective manner. processing capacity is about 50m3/h in the field for one dewatering unit. the dewatered sludge is discharged into a cuttings tank and the cleaned effluent is returned to storage or the active mud system. to determine the compatibility, between water coming from the dewatering operation and water base drilling fluids, the rheology needs to be checked. the water will be used as make up water to mix mud or to dilute the mud system. in this case, we have to make sure that the residual polymer concentration is not going to affect the mud system in a negative manner i.e.flocculating/thinning the mud, which can lead to a complete loss of the mud system or even loss of the well. the compatibility test procedure as below: firstly, collect mud from active system and run api mud rheology. then mix 50 % of water (175ml) and 50% of mud from active system (175ml) for a final volume of one equivalent barrel, let it mix for minimum 15 minutes at low speed. run and report api mud rheology. report mud appearance for example, thick, thin, flocculated, etc. fig 15 discharge water the acceptable water is that water that does not has a change in rheology of more than 50% in the reported values.there are total 7720m3 discharge waste water and 4187m3 for reuse such as an appraisal well aznn-003. 6.evaluation of site waste management many factors contribute to an site waste management, such as 1200m for 17-1/2” large hole in 7days to increase cutting volume, salt water cut in 12-1/4” hole, heavy rain in winter and so forth in n.azadeagn field. some problems and challenges are not completely included in the planned waste management design, so site expereices and lessons should be thoroughly evaluated for the future implementation. firstly, inadequate preparation is one of influence factors to the performance of the drilling cutting removal processes especially for faster footage in 17-1/2” large hole than before. when 8 drilling rigs start to spud together, many drilling cutting can not be dry or transported for pavage in absence of enough waste treatment equipment and trucks. although the rate and composition of solids discharge at each stage of the removal process are monitored and evaluated, more equipment for improving bulk discharge rates should be provided for 17-1/2” large hole. on the other hand, very low civil work efficiency or heavy rain in winter brings serious influence for ongoing pads construction duration. some cluster well pad costs more than 11 months when 5 months are nomarly estimated in civil work plan. so, some landfill measures also are taken for drilling solids in short of new pad& road for pavage. secondly, some waste water such as spilled or improperly disposed drilling wastes, drity water from drilling floor, contaminating water, cement water etc are more than expected, so the