Mangala field is one of the largest discovered group of oil fields in Barmer Basin, Rajasthan, India. The fields contain medium gravity viscous crude (10-40cp) in high permeability (1-5 Darcy) sands. Currently the field is on polymer flood to improve the sweep efficiency during enhanced oil recovery. As expected, polymer breakthrough was observed in producer wells. However, this has resulted in challenging well interventions due to polymer/scale depositions in the wellbore and Downhole artificial lift equipment. This issue has surfaced due to mixing of produced polymer with scales, wax and various bivalent ions. Major concerns due to polymer deposition included, fouling of artificial lift system, decrease of well uptime and decreased efficiency of jet pump (type of artificial lift). Reverse jet pumping, where power fluid is pumped through annulus and production is taken through tubing, is the most common method of artificial lift for the field. During jet-pump redressing, polymer deposition has been observed in the Body X-over (Reservoir liquid path), check valve assembly, throat and spacer nozzle to throat inside jet-pump. Continuous chemical injection was tried and proved to be a technical success, but it was not cost effective. Hence data-based predictive approach for pre-emptive changeovers of Jet Pump was developed. The developed model is "intelligent". It learns from every newly logged event and auto correct its approach of marking the risk levels of a well. The well intervention history of over 1000+ well interventions in 170+ oil producers were recorded. The recorded data was then studied for sensitivities such asnumber of interventions viz. – wire scratcher run and Jet pump retrieval / installation runsObservations on severity of polymer/scaling issueChemical soaking requirement of chelating agents such as EDTA, DTPA for dispersing polymer,Well downtimeHistories of slickline fishing events, stuck BHAs. The data was then analyzed and used to create a well intervention risk matrix which in turn classifies all 170 wells into low, moderate and high-risk wells. This approach also sets a predictive timeline for individual well failures. The model/approach is intelligent enough to learn from operational history and auto-corrects itself every time a new event is logged. This paper addressesFormation of agglomerated polymer lumps due to scale formation inside well completions.Deposition of polymer layer inside completion equipment and production tubingDetailed stepwise analysis of over 1000+ well intervention in oil producers producing oil and polymer mixed water.Basis of logic for creating a predictive sheet for Jet Pump change outs.Predict optimal Intervention frequency for every well to de-risk jet pump change slickline interventionDetermination of critical wells which have severe deposition issuesTracking of rigless units’ efficiency and planning, especially highly mobile slickline unitOptimize production from fieldPlan for chemical soaking in tubing of wells where polymer and scale deposition are predicted. This paper gives a new approach to those E&P companies who are producing their field on Jet pumps and are using Polymer flood as recovery mechanism. The use of this approach from day zero in such fields would help to create a customized analytical approach for the field and hence reduce production downtime.
This abstract is submitted as an addendum to SPE-188853-MS, which deliberate about Improving Sweep Efficiency by Zonal Isolation Using High Expansion Ratio Inflatable Plugs. "M" field contains medium gravity viscous crude (10-20cp) in high permeability sands. Application of EOR technique is considered pivotal in sustaining the plateau production rate and maximizing the ultimate recovery from this field. "M" field is currently under polymer flooding with wells completed in a 5-spot pattern. The high viscosity crude in this field, with an unfavorable mobility-ratio with water, mandated the need to switch from water to polymer flooding. Even though good sweep improvement was observed in most of the patterns, a few pattern producers didn't respond to polymer flood as expected. They exhibited poor sweep efficiency which resulted in bypassed oil and early water/polymer breakthrough. The poor sweep efficiency adversely affects the project economics by reducing the Expected Ultimate Recovery (EUR) and increasing the opex associated with produced water handling. Paper SPE-188853-MS outlined how the installation of "high expansion ratio inflatable plugs" in the pattern producers, improved sweep efficiency. This paper adds further case studies to it, carrying forward the success of these Plugs. Moving onward the process of isolation based on detailed analysis of pattern flood producer wells which were shut-in, due to high water-cut and production handling constraints. Saturation log were carried out to locate the poorly swept sand zones. Also, since most of the wells are sub hydrostatic and exist on artificial lift. N2 assisted PLT were carried out to identify high water cut zones and accordingly zonal isolation of such high water cut zones were planned. Temporary isolation was required to accommodate plans for future ASP (Alkaline Surfactant Polymer) flooding. Both mechanical and chemical isolation methods were explored and accordingly well candidates were identified for each of the methods for isolation. Mechanical isolation methods are discussed in the paper (chemical isolation being discussed in a separate paper). Last paper gave insight about plug passing through a minimum ID of 2.3" and set in a 7" production casing. After this campaign, more candidates with plug setting section of 9-5/8" Casing & 4-1/2" Screens were selected. Plug setting with Coil Tubing & E-line were explored and executed. The jobs were successfully conducted in around 30 producer wells. The isolation resulted in a 3-4-fold increase in the instantaneous oil production with around 40% drop in produced water cut. This demonstrated how the treatments improved the selective drainage of the poorly swept sands by allowing preferential movement of flood front in these sands. To support selective treatment of injector wells for sweep bypassed oil sands, through tubing inflatable straddle packer acidization jobs are being planned to further increase the injection in poorly swept zones.
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