Scale deposition, either in the formation, well bore or in the production facilities is a challenging problem in the petroleum industry. Scale problems are generally associated with the deposition of inorganic minerals, such as calcium carbonate (CaCO3) and sulfates of calcium, strontium and barium. Downhole mineral scaling is either a product of self-scaling of the formation water (FW), (carbonate scale associated with changes in pressure and/or pH) or the mixing of incompatible waters (FW and injection water) with elements of other wellbore fluids or other minerals. The cost of scale buildup can be high, both in terms of deferred production and necessary remedial treatments. Depending on the nature of the scale and the fluid composition, the deposition can take place within the reservoir, near the wellbore perforation tunnels which causes formation damage, or in production facilities subsurface and on surface with severe operational problems. The Cased Hole Gamma Ray measurement has been proven quite effective to detect the presence of scale, due to radioactive content proven by the Scale XEM/EDAC analysis. The Scale solubility analysis has proven more than 95% of the sample, are soluble in 10%-HCl based acid. Finally, the two case studies of Miano field have brought a new game changer for operations, to enhance the gas production. It is based on historical well observation, since no water production had been observed at the surface in one of the case study, so Scale was not considered to cause the production decline. Therefore the method of Cased Hole Gamma Ray measurement can be in some cases the only indication of scale build-up if other indicators are missing. Furthermore it’s also an effective method to prove scale build-up inside perforations if hole is fully accessible. This paper describes the buildup of scale, its detection and its successful removal with coiled tubing in high temperature gas wells of Miano Field. Furthermore it will show some lab results, the execution and evaluation the results of a successful operation, which resulted in a restoration of high productivity.
With current demand for gas at historic peak, any decrease in production due to deposits of scale within tubing is the most troublesome for any E&P company. Statistically 28% of time it is the scale in well that hinders producing it at optimum rate. "Carbonate" and "Sulfate" scales are most common of mineral scales that form in wells. Carbonate scales are generally tackled by wellbore cleanout with acid or by using scale inhibitors to slowdown scale deposition process but none of these solutions solve the problem on permanent basis. Sulfates scales are generally very hard to remove through acid job and usually chemical chelants are used to control sulfate scales.The major production enhancement challenge faced in well 'X' was to permanently mitigate severe scale build up issue in tubing for optimum production performance. This paper presents how these challenges were faced and overcome by using ClearWELL * unit, resulting in stable and continuous production.A scale study was conducted by OMV laboratory in Vienna to identify the scale build up mechanism and solutions for its mitigation. The study confirmed that minor pressure decrease at formation temperature promoted water transfer into the gas phase, if water rate is low compared to gas rate, this can result in complete evaporation and formation of precipitate leading to scale build up (mainly calcite). To reinstate production, repeated wellbore cleanouts with coiled tubing using diluted HCl (7.50%) were thought to be the temporary solution in fighting CaCO 3 scales.ClearWELL unit was commissioned at well 'X' x-mas tree, which is currently under pilot testing. It is an electromagnetic device which continuously generates electronic dipole that induces a randomly varying high frequency electric field throughout the entire piping system. The electric field * ClearWELL is an electromagnetic device. generated by device forces homogeneous crystal formation in suspension rather than on metal surfaces. Scale crystallizes in suspension and is carried away with gas water mixture.During last 5 months of its pilot testing, results achieved so far are promising. Stable and no lost production added a reasonable value to the producing asset and saved huge revenue loss to the company.
Well ‘X’ was drilled in a gas condensate reservoir located in Kirthar fold belt with the primary target of P & R formations. During CIT of P formation in April 2012 the well was tested at 4.03 MMscfd gas, 1543 STB/day condensate & 1670 bbls/day water at a FWHP of 309 psi. Available production logging surveys with water & gas holdup tools were performed twice to identify the water producing zones; however the results were inconclusive as commonly used production logging tools are able to identify production contribution only across the perforated intervals and cannot detect behind casing communication and flow within reservoir. The well had been shut-in as plant was not ready for tie-in, so opportunity was taken to conduct HPT-SNL suite (in memory mode with slickline) in August 2013 which resulted not only in identifying the water producing zones but also confirmed hydrocarbon influx zones above perforated interval and flow behind casing from above perforated interval. HPT is a high precision temperature tool with resolution of 0.003oC and response time less than 1 second to capture any small flow, whereas SNL is spectral noise logging tool which can scan noise spectrum through multiple barriers for evaluation of any cross flow behind casing and leakages. Based on HPT-SNL results, water shut-off was performed which considerably reduced water production (from 1318 to 520 bbls/day), consequently reducing WGR (from 628 to 244 bbls/MMscf) with no change in gas rate whereas increase in condensate production was observed (from 330 to 855 STB/day). This paper describes the complete case study of diagnostic logging followed by remedial work to optimize the producing asset value.
This paper describes the success story of the first water shut off treatmentusing Engineered Micro-cement Slurry (EMS) through Coiled Tubing in Pakistan.The well was an oil well producing from multiple zones, but mainly the lowerzone (C-Sand). Due to high water cut, it was decided to isolate the C-Sand andto produce only from the upper perforations (A/B Sands). Based on economics andtechnical feasibility, water shut off treatment through a cement plug wasselected to isolate the C-Sand zone. 148ft of cement plug was squeezed andspotted across the C-Sand through coiled tubing using conventional cementslurry. After setting the cement plug, water cut was reduced by 23% and thewell initially produced up to 380bopd from the A/B Sand. After 3 monthsproduction, water cut level increased drastically back to 100%. A slickline runconfirmed that the cement plug had failed and top of cement dropped 48ft fromits original depth. It was suspected that the plug failed due to possiblecontamination in the cement, which enabled water to channel up across the plug.A remedial cement plug through coiled tubing was subsequently set, but thistime using EMS slurry to ensure that any channels in the previous plug werecemented and ensuring that the perforations were sealed off completely. The jobwas conducted successfully and the water cut was reduced by 25%, with initialproduction of 500bopd from the A/B Sands. Introduction Excessive water production is a major concern in the production of oil andgas. High water production can contribute surface problems (water handling anddisposal) and downhole problems such as scale deposition, emulsion, asphaltene, sand production, corrosion, etc. In many areas in Pakistan, field waterproduction exceeds hydrocarbon production. The majority of wells with waterproduction problems in Badin are producing through artificial lift. Over time, water production continues to increase until wells cease to produce due to highwater loading or reach their economic limit and are shut it until furtherintervention is decided.
This paper describes the success story of the first water shut off treatment using Engineered Micro-cement
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