Donald E. Menzie

Experimental Studies of In-Situ Microbial Enhanced Oil Recovery

Experiments were conducted to study the feasibility of using microorganisms in EOR, particularly for the correction of permeability variation. The use of microorganisms requires the ability to transport viable cells as well as the nutrients required for cellular growth through reservoir formations. Nutrients such as glucose, peptone-protein, and phosphate and ammonium ions were transported through brine-saturated Berea sandstone cores in amounts sufficient to support microbial growth. Viable bacterial cells were transported through sandstone cores of 170-md permeability. Less than 1% of the influent cell concentration was recovered in the effluent, indicating a high degree of cell retention inside the core. The addition of nutrients to these cores and subsequent incubation to allow for microbial growth resulted in permeability reductions of 60 to 80%. These data show that the growth of microorganisms significantly reduces the permeability of porous rock.

An Approach to the Optimum Design of Sucker-Rod Pumping Systems

Sucker-rod pumping system design is often a trial and error process. Many simplifying assumptions are used which may not be consistent with the well conditions. This paper presents a new methodology for the optimum design of pumping unit systems. In this approach, plunger diameter, polished rod stroke length, pumping speed and pump intake pressure are chosen as basic design variables. Production rate and rod string taper are determined by an iteration algorithm which systematically couples well inflow performance and vertical flow effects into the design process. Polished rod load, peak gear box torque, polished rod horse power and counterbalance effect are also determined at the end of the iteration calculation. Different design objective functions can be used to rate the pumping modes. Thus, the optimum design of pumping unit systems becomes a matter of solving for the combination of the four basic design variables which maximize or minimize an objective function within the limitations of available equipment by a mathematical programming method.

Well Injection Tests Of Non-Newtonian Fluids

The flow behavior of polymer solutions and micellar solutions in the reservoir was analyzed using the steady-state radial flow test (Hall plot). Injectivity data from 3 tertiary recovery field tests were used to obtain the Hall plots. These field tests are micellar-polymer floods and include the Bradford field test in Pennsylvania, the N. Burbank Unit test in Oklahoma, and the El Dorado field test in Kansas. The Hall plots for the micellar-polymer floods were then compared to the Hall plot for water. This was to determine the effect of non-Newtonian rheological behavior on the flow of the micellar and polymer solutions in the formation. Since the slope of the Hall plot is proportional to the reciprocal of the mobility, the Hall plot is a function not only of the viscosity of the injected fluid, but also depends on the effective permeability to the injected fluid. Therefore, the Hall plot was used to determine if near-wellbore plugging had occurred, if the fluid had behaved as a non-Newtonian fluid, if the effective permeability to the injected fluid had increased due to increased miscibility or if the permeability had been reduced due to the flow of the polymer solution. (10 refs.)

A New Method of Coating Oilfield Core for Laboratory Studies

A new method has been developed for coating oilfield core for laboratory studies. It consists of applying a steel coating and aluminum wraps around the outer surface of a core. The strength of the coating, the short time needed to apply it, and its low cost are the major advantages of this new method.

The Effect of Polymer Additives on Oil Recovery In Conventional Waterflooding

This paper discusses the results of a laboratory investigation utilizing water soluble polymer additives in conventional waterflooding. A conventional waterflood was conducted through each core utilizing a 50,000 ppm brine solution as the displacing medium. Also, a polymerflood was conducted through each core utilizing a 0.05% polymer solution as the displacing medium. The results of this investigation indicate that oil recovery at breakthrough and that ultimate oil recovery was increased when polymer solution was used as the displacing medium. Expressed as a percent of the original oil in place, the recovery at breakthrough ranged from 7.60 to 10.76% higher when compared with a conventional waterflood. Increased oil recovery after 2.5 pore volumes of fluid were injected ranged from 3.3 to 10.0%. It was concluded from this investigation that increased oil recovery was a result of the viscosity effect of the polymer additive.

A method of measuring dispersivity and its use in slug size estimation in a miscible flooding process

The dispersion phenomenon governs mixing of two miscible fluids, one displacing another, in a porous medium. In such a medium, two basic mechanisms cause the dispersion process to occur, as a result of the irregular nature of the interstitial velocity field forced on the flowing fluid by the heterogeneous porespace (Sahimi et al., 1986). (1) In a disordered porous medium, flowpaths become disrupted and continually separate and rejoin at the junctions of flow passages. This leads to a wide variation in length of flowpaths traversing the system, which is considered to be the kinematic mechanism of dispersion. (2) As a result of changing pore geometry, orientation, and local pressure gradient of a flowpath, the speed along the flowpath varies considerably as the medium is traversed. These two basic mechanisms cause a concentration front of fluid particles to spread as it advances through the system. The extent of the spread of this front depends upon the dispersivity of the porous medium. The main objective of this experimental study is to develop a s tandard technique for measuring dispersivity of actual reservoir rocks by conducting tests on representative core samples. Correlations of dispersivity with other reservoir rock characteristics were also investigated. The first step was to establish a s tandard technique for measuring the dispersivity, c~d, of reservoir rocks. Various techniques were tried on sandpacks and core samples of actual reservoir rocks. A new core-mounting method, using liquid metal (Menzie et al., 1988), has been developed during this study. Cores mounted with this technique can be safely used with highpressure displacements. Two techniques for measuring effluent concentrat ions were used: (1) conductivity meter, and (2) refractometer. More accurate and reliable results were obtained by the refractometer technique. Other techniques, such as distillation, tracers, ion analyzer, etc., were not used as they required different laboratory set-ups and as the refractometric system yielded satisfactory results. Recently, brine (1 wt% NaC1) was introduced for initial saturation, and a further effort has been made to study the effect of connate water saturation on measurement of the dispersivity of a rock. A simple, economic, and safe method has been developed as part of the standard experimental method for the determination of dispersivity. In conventional oilfield operations, as water from an injection well moves through the po-

Analysis Of Fracture Treatment Pressure Fall-Off Data

This paper discusses the results of a study made to determine if surface pressure fall-off data existing after a fracture treatment could be correlated to reservoir flow capacity. The theoretical aspects of pressure dissipation away from the fracture during and after the treatment are considered, and a method is proposed to calculate reservoir flow capacity from these data. This method is an adaptation of the procedure used for estimating reservoir injection capacity in water injection wells. Field data from 5 fracture treatments are presented, and calculated flow capacities are compared with existing knowledge of reservoir flow capacity in the particular fields. It was concluded that analysis of fracture treatment pressure fall-off data may be useful in determining reservoir flow capacity. Analysis of these data may also be helpful in evaluating the results of fracture treatments.