Robert D. Sydansk

A strategy for attacking excess water production

This paper describes a straightforward strategy for diagnosing and solving excess-water-production problems. The strategy advocates that the easiest problems should be attacked first and that diagnosis of water productionproblems should begin with the information already at hand. A listing of water-production problems is provided, along with a ranking of their relative ease of solution. Although a broad range of water-shutoff technologies is considered. the major focus of the paper is when and where gels can be effectively applied for water shutoff.

A Newly Developed Chromium(III) Gel Technology

Laboratory testing of a recently developed chromium(III) (Cr(III)) gel technology is reported. The gels can be used in conjunction with a number of oilfield treatments. The single-fluid acrylamide-polymer/Cr(III)-carboxylate aqueous gels are formed by crosslinking acrylamide polymer with a Cr(III)-carboxylate-complex crosslinking agent. Representative gel compositions and associated gel properties are discussed.

More Than 12 Years' Experience With a Successful Conformance-Control Polymer-Gel Technology

In this paper, we discuss and describe our extensive experience with the widely applied and quite successful Cr(III)-carboxylate/acrylamide-polymer (CC/AP) gel technology for use in oilfield conformance-control, sweep-improvement, and fluid-shutoff treatments, along with briefly reviewing the gel technologys development. Chromic triacetate is the oftenpreferred chemical crosslinking agent used in conjunction with this polymer-gel technology. The CC/AP gel technology, which was conceived in late 1984, is characterized as having a robust gel chemistry and as being highly insensitive to petroleum reservoir environments and interferences. This gel technology has been employed in over 1,400 conformancecontrol treatments worldwide. Highlights of illustrative field applications and results involving the CC/AP conformancecontrol gel technology are presented. An overview of what a decade-plus of experience in developing and applying the CC/AP gel technology has taught us is discussed. This includes discussion of: classifying and distinguishing conformance problems and treatments, attributes of good candidate wells and well patterns for gel conformance-control treatments, requirements that must be met in candidate wells and well patterns in order to achieve success, gel treatment elements that must be successfully implemented in order to achieve success, guidelines where conformance polymer-gel treatments are most successfully applied, risks and pitfalls of gel conformance treatments, and quality control issues.

Colorado Green River Formation oil shale as viewed by pulsed n.m.r.

Abstract Wideband proton pulsed n.m.r. techniques have been applied to selected Colorado Green River Formation oil shales. Among the various parameters generated by this technique, one correlates with total organic matter contents and another correlates with Fischer assay oil yields. The free induction decay (FID) amplitude quantitatively measures total oil shale proton contents when 1. (1) the amplitude is extrapolated up to the midpoint of the radio frequency pulse, and 2. (2) an adequate trigger repetition rate ( t r ) is used. A 1 s value of t r , within experimental precision, masks the crystalline inorganic protons. The maximum FID amplitude with a 1 s t r correlates with the total organic matter content. T 1 decays for the organic matter have two relaxation components. The fast component has relaxation times ⪡ 5 ms. Maximum FID amplitudes using a 1 s t r , reduced by the fraction of protons with the fast T 1 decays, correlate directly with Fischer assay oil yields. This T 1 correction factor, thus, reflects the organic matter unrecoverable as oil by the Fischer assay. The reported procedure cannot alone resolve oil-shale free and clay interlayer water protons from the organic protons. This work, along with literature references, shows these protons to be present in minor quantities as compared to the organic proton content of commercial oil shales. If such protons should be present in significant quantities, their concentration can be greatly reduced by finely crushing the oil shale and drying at 110 °C overnight.

A Strategy for Attacking Excess Water Production

This paper describes a straightforward strategy for diagnosing and solving excess water production problems. The strategy advocates that the easiest problems should be attacked first and diagnosis of water production problems should begin with information already at hand. A listing of water production problems is provided, along with a ranking of their relative ease of solution. Conventional methods (e.g., cement, mechanical devices) normally should be applied first to treat the easiest problems— i.e., casing leaks and flow behind pipe where cement can be placed effectively and for unfractured wells where impermeable barriers separate water and hydrocarbon zones. Gelant treatments normally are the best option for casing leaks and flow behind pipe with flow restrictions that prevent effective cement placement. Both gelants and preformed gels have been successfully applied to treat hydraulic or natural fractures that connect to an aquifer. Treatments with preformed gels normally are the best option for faults or fractures crossing a deviated or horizontal well, for a single fracture causing channeling between wells, or for a natural fracture system that allows channeling between wells. Gel treatments should not be used to treat the most difficult problems—i.e., three-dimensional coning, cusping, or channeling through strata with crossflow.

Rheological properties of fluids composed of an alkylbenzene sulfonate, decane, cyclohexanol, and water

Abstract Rheological properties of a concentrated surfactant system were determined. Flow curves for a fluid composed of an alkylbenzene sulfonate, hydrocarbon, water, and cosurfactant were obtained as a function of the amount of water added to the system. All fluids were optically clear and phase stable. Compositions that can be classified as oil-external microemulsions were found to exhibit Newtonian flow behavior. Non-Newtonian flow was observed for those compositions that were in the oil-external to water-external transition region. Certain compositions in this region showed a discontinuity in the flow data suggesting a sudden transition from the lamellar structure of the phase inversion region to spherical droplets of water-in-oil.

Elevated-Temperature Caustic/Sandstone Interaction: Implications for Improving Oil Recovery (includes associated papers 11348 and 11548 )

At an elevated temperature of 85 C, caustic in the form of sodium hydroxide solutions strongly interacts with sandstone, resulting in a significant dissolution of the more susceptible silicate minerals and in hydroxide-ion consumption. Therefore, when designing secondary and tertiary oil-recovery caustic floods using sodium hydroxide, silicate-mineral dissolution should be considered as contributing to caustic consumption. Because the dissolution interaction is kinetically limited and the kinetics are slow at ordinary formation temperatures, care should be taken in scaling laboratory caustic floods to field conditions for applications involving long-duration and low-concentration sodium hydroxide floods. 35 references.

When and Where Relative Permeability Modification Water-Shutoff Treatments Can Be Successfully Applied

Summary This paper provides guidance on when and where relativepermeability-modification/disproportionate-permeability-reduction (RPM/DPR) water-shutoff (WSO) treatments can be successfully applied for use in either oil or gas production wells. When properly designed and executed, these treatments can be successfully applied to a limited range of oilfield excessive-water-production problems. When these treatments are applicable, they may be placed using bullhead injection (not requiring mechanical zone isolation)—a very favorable feature. However, there are a substantial number of limitations and possible pitfalls relating to the successful application of RPM/DPR WSO treatments. First-time application by an inexperienced operator should be considered a somewhat high-risk undertaking. In order to successfully treat unfractured production wells (i.e., radial flow through matrix rock into the well) that are fully drawn down, the oil and water zones should not be in pressure communication and the oil-producing zone(s) must be producing at 100% oil cut (dry oil). When treating unfractured and multizoned production wells that are not fully drawn down, the well’s long-term oil-production rate can be increased if the post-treatment drawdown is increased substantially. Treatments that promote short-term (transient) decreased water/oil ratios can, in principle, be applied to many unfractured production wells (that are not totally watered out) in matrix-rock reservoirs. However, these latter treatments must be custom designed and engineered on a well-by-well basis. Furthermore, for most wells, the performance and the economics of such transient WSO treatments are generally marginal. An attractive application of RPM/ DPR WSO treatments is the use of robust pore-filling gels in the matrix reservoir rock that is adjacent to a fracture(s) when oil and water is being co-produced into the treated fracture.