John M. Tinsley

A New Method for Providing Increased Fracture Conductivity and Improving Stimulation Results

The success of a fracturing stimulation treatment is dependent on the strength and distribution of the propping agent used to prevent the created fracture from closing after the treatment. A method is presented in which the proppant is distributed in a planned spaced manner throughout the fracture separated by stages of flush fluid. In this method, the proppant stages function as pillars to hold the fracture surfaces apart so the fluid may flow between the proppant beds. The flow capacity of an open crack is several orders of magnitude greater than that of a bed of proppant. The design of the staging is discussed and the mathematical model it is based on is given. Treatments in the field are discussed and results are given for 2 areas. Significant production increase values have been realized. (12 refs.)

Vertical Fracture Height-Its Effect on Steady-State Production Increase

A family of curves for predicting production increase due to a vertical fracture has been available for some years. These curves were developed from an electric network analog model and reflect unsteady-state conditions. These were specific for a particular fracture length to drainage radius ration. This model was based on the fracture height being equal to the reservoir height. If the fracture height or propped portion of the fracture predicted by proppant transport relationships is less than the reservoir height, the aforementioned curves are not applicable. In this study, data taken from a steady- state electrolytic model was used to develop curves for production increase as a function of fracture height, reservoir height, fracture length, drainage radius, fracture flow capacity, formation permeability and wellbore radius. This work may allow a more complete evaluation of the effect of fracturing parameters, such as injection rate, propant size, proppant concentration, and viscosity or productivity increase. (10 refs.)

Effect of Treatment Parameters on the Geometry of a Hydraulic Fracture

The parameters influencing the geometry of a hydraulic fracture are divided into 3 categores: (1) those upon which there is no control, such as Youngs modulus and Poissons ratio of the formation, far-field stress and the reservoir pressure; (2) those which are easily controlled such as treatment-fluid viscosity and time; and (3) those which are partially changeable, like fluid leak-off and injection rate. A study is made of the effects of each individual parameter on the geometry of a hydraulic fracture. Based on the findings reported, it is concluded that at the present time, the treatment-fluid viscosity appers to be the most promising factor for influencing the geometry. Increasing the viscosity has 2 effects. Directly, it increases the width of the generated fracture, thus yielding better conditions for the transportation of the propping agents. Indirectly, it reduces the volume of fluid lost as leak-off. Another important conclusion is that the computed fracture geometries are, to a large degree, influenced by the assumed value of the fracture height. A reasonable geometry can be obtained only if one assumes a reasonable value for the fracture height.

Design techniques for chemical fracture squeeze treatments

The chemical fracture squeeze technique, combining the effects of a fracturing treatment and a squeeze operation, has been more successful than conventional squeeze operations. Knowledge derived from well stimulation and reservoir engineering research can provide a means of predicting the effective life of such a treatment. Analysis of theoretical equations and concepts developed allows selection of improved treatment techniques based on specific formation conditions. These equations have been computerized to allow rapid determination of treatment recommendations. Such chemical fracture squeeze techniques can be utilized in the economic application of corrosion inhibitors, emulsion breakers, paraffin and scale inhibitors. The application of these techniques in conjunction with fracturing treatments is shown to be very effective. The results of field treatments are given. (15 refs.)

Gas well deliverability improved by planned fracturing treatments

Deliverability from thousands of gas wells has been improved materially by hydraulic fracturing. Both flowing rate and wellhead pressure frequently increased substantially. In many cases production following treatment has been several fold greater than that obtained upon initial completion. Where it has been possible to make detailed study of well data and plan treatments based thereon, results have been quite gratifying. Specific study of cores from individual wells has provided better information for selection of more appropriate fracturing techniques, procedures, and chemicals. Different factors are discussed which should be considered in pre-planning fracturing treatments and some field examples are cited. (49 refs.)