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Collaborating Authors
Results
Chelating Agent for Uniform Filter Cake Removal in Horizontal and Multilateral Wells: Laboratory Analysis and Formation Damage Diagnosis
Al-Ibrahim, Hussain (Saudi Aramco) | AlMubarak, Tariq (Saudi Aramco) | Almubarak, Majed (KAUST) | Osode, Peter (Saudi Aramco) | Bataweel, Mohammed (Saudi Aramco) | Al-Yami, Abdullah (Saudi Aramco)
Abstract An impermeable mud cake layer, created on the formation face while drilling may be favorable for drilling operations but detrimental to well productivity. In vertical high pressure wells the layer is cleaned out while flowing back the well at adequate pressure drawdown. On the other hand, low pressure differential at the sand face in horizontal wells makes well cleanup treatments a necessity. Not all filter cake components are acid soluble. Commonly used inorganic acids and oxidizers are very reactive and cause uneven filter cake removal, which can affect the well's performance. As a result, there was a need to evaluate slow-reacting chemicals that can produce delayed uniform filter cake removal in horizontal wells. These treatment chemicals vary from the nonreactive acid-free microemulsion fluid systems to the weak organic acids, acid precursors, enzymes and chelating agents. The objective of this paper is to evaluate two chelating agent based treatments, NTA and EDTA, as filter cake removal treatments for a sandstone reservoir utilizing oil based mud (OBM) drill-in fluid (DIF) in Saudi Arabia. Coreflooding experiments were run under reservoir conditions to evaluate fluid-rock interaction. In addition, fluid-fluid compatibility was conducted between chelating agent and drill-in fluids base brines and between the chelating agent and formation fluid using high temperature, high pressure (HTHP) see-through cell. Solubility and static fluid-loss tests were conducted to evaluate the filter cake removal efficiency. Experimental results indicated that the NTA-based treatment was effective in removing up to 91% of the filter cake uniformly after soaking treatment for 24 hours. Fluid-fluid compatibility tests showed that the NTA-based chelating agent, when mixed with reservoir fluids, was free from precipitation or emulsion. On the contrary, mixing the chelating agent with the DIF carrier brine resulted in severe precipitation of insoluble permanently damaging byproducts. The laboratory study also observed that pH has a direct proportional relationship with the amount of precipitation. EDTA-based treatment results showed a removal efficiency of 93% after soaking treatment for 90 hours. Fluid-fluid compatibility tests showed that the EDTA-based treatment, when mixed with OBM DIF was free from precipitation or emulsion. On the contrary, mixing the chelating agent with the reservoir formation water resulted in severe precipitation of insoluble permanently damaging byproducts.
- Well Drilling > Drilling Operations > Directional drilling (1.00)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (1.00)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid management & disposal (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology (1.00)
Abstract The huge resources of unconventional gas worldwide along with the increasing oil demand make the contribution of unconventional gas to be critical to the world economy. However, one of the major challenges that operators face to produce from unconventional resources is commercial stimulation technique that creates sufficient stimulated reservoir volume. Unconventional reserves trapped within very low permeability formations, such as tight gas, or shale formations, exhibit little or no production, and are thus economically undesirable to develop with existing conventional recovery methods. Such reservoirs require a large fracture network with high fracture conductivity to maximize well performance. One commonly employed technique for stimulating low productivity wells is multi-stage hydraulic fracturing, which is costly and typically involves the injection of high viscosity fluids into the well. Fracturing fluid by itself could form a damaging material for the fracture due to high capillary forces. Thus, additional needs exist for an economical method to enhance production within a tight gas formation. This paper discusses a new stimulation method to increase stimulated reservoir volume (SRV) around wellbore and fracture area, and therefore, improve unconventional gas production. The method entails triggering an exothermic chemical reaction in-situ to generate heat, gas and localized pressure sufficient to create fractures around the wellbore. In controlled experiment, chemical reactants were separately injected into core samples with a minihole and upon mixing inside the core, an exothermic chemical reaction occurred and the resultant heat and gas pressure caused macro-fractures. NMR-porosity imaging showed significant increase in macro pores throughout the core. Additionally Large scale experiments using cement blocks with a simulated wellbore cavity were performed. Once the wellbore was filled with the chemicals and upon introducing a triggering catalyst an in-situ chemical reaction took place which generated heat and gas with sufficient pressure to cause shear fractures in the surrounding rock. These experiments showed extensive fractured and shattered pieces and also provided preliminary design requirements for a field test. The chemical reactants then incorporated into a fracturing gel to simulate creating additional fractured from the main induced hydraulic fracture. The results were very encouraging and the generated high temperature and pressure caused the gel to break thus it is concluded that this technique effectively contribute to fracture cleanup in addition to creating required SRV. The experiments were very successful in proving the new concept of generating SRV in tight gas well and the developed stimulation technique is fairly easy to implement in the field.
- North America > United States (0.69)
- Asia > Middle East > Saudi Arabia (0.69)
- Research Report > Experimental Study (0.86)
- Overview > Innovation (0.67)
- Research Report > New Finding (0.66)
- Research Report > Strength High (0.54)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.56)