Laboratory Development and Field Testing of Succinoglycan as a Fluid-Loss-Control Fluid
- Hon Chung Lau (Shell Development Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- December 1994
- Document Type
- Journal Paper
- 221 - 226
- 1994. Society of Petroleum Engineers
- 5.2 Reservoir Fluid Dynamics, 5.4.10 Microbial Methods, 2.4.5 Gravel pack design & evaluation, 2.2.2 Perforating, 2.7.1 Completion Fluids, 1.6 Drilling Operations, 2.2.3 Fluid Loss Control, 2 Well Completion, 2.4.3 Sand/Solids Control, 4.3.1 Hydrates, 1.8 Formation Damage
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Research has shown that the biopolymer succinoglycan possesses a unique combination of desirable properties for fluid-loss control, including ease of mixing; cleanness; shear-thinning rheology; temperature-insensitive viscosity below its transition temperature, Tm; and adjustable Tm over a wide range of temperatures. Because succinoglycan is a viscous fluid, it relies solely on viscosity to reduce fluid loss. It does not form hard-to-remove filter cake that can cause considerable formation damage. On the basis of these findings, we used succinoglycan successfully as a fluid-loss pill before and/or after gravel packing in >100 offshore wells. Calculations based on laboratory-measured rheology and field experience have shown succinoglycan to be effective in situations where hydroxyethyl cellulose (HEC) is not. Even fluid loss >40 bbl/hr was reduced to several bbl/hr after application of a properly designed succinoglycan pill. Most wells experienced no production problem after completion.
Fluid-loss control is often crucial to successful well completions. It is often needed after perforating and/or after gravel packing. Excessive loss of completion fluid into the formation can be expensive (in the case of heavy brines), can prevent tripping in and out of the hole, can cause formation damage (if the completion brine is damaging), and can delay hydrocarbon production after completion. Various fluid-loss-control materials have been used. Most are either filter-cake-forming or viscous materials.
Filter-cake-forming materials (e.g., sized salts or carbonates and oil-soluble resins) stop or reduce fluid loss by forming a low-permeability filter cake at the formation sandface or at the mouth of the perforations if they are prepacked. Some crosslinked polymeric gels may also be considered as filter-cake-forming materials because they control fluid loss by forming a leathery skin at the sandface that essentially acts as a filter cake. One advantage of these systems is their ability to control fluid loss over several days or longer. One disadvantage is that the filter cake is often difficult to remove. If an internal breaker is not used, contact and/or soaking with a cleanup solution is needed to remove the filter cake. Insufficient cleanup often results because of viscous fingering or loss of cleanup solution to a thief zone. Putting the well on production may not be sufficient to remove the filter cake from the entire completion interval.
The most commonly used viscous fluid-loss-control material is HEC. The advantages of HEC are that it is cheap and can dissolve in both low- and high-density brines. However, hydration of HEC in high-density brines may require extended shearing time and/or heat. HEC has at least two disadvantages. First, the quality of the HEC pill depends critically on its preparation. Improper pH adjustment or inadequate mixing may result in damaging fisheyes (i.e., partially hydrated polymer particles). Thus, shearing and filtering often is recommended for quality control. Second, HEC solution viscosity decreases with increasing temperature (Fig. 1), making it less effective at controlling fluid loss at elevated temperatures.
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