Measurements of Hydraulic-Fracture-Induced Seismicity in Gas Shales

Methods and systems are provided for evaluating subsurface earth oil and gas formations. More particularly, methods and systems are provided for determining reservoir properties such as reservoir transmissibilities and average reservoir pressures of formation layer(s) using quantitative refracture-candidate diagnostic methods. The methods herein may use pressure falloff data from the introduction of an injection fluid at a pressure above the formation fracture pressure to analyze reservoir properties. The model recognizes that a new induced fracture creates additional storage volume in the formation and that a quantitative refracture-candidate diagnostic test in a layer may exhibit variable storage during the pressure falloff, and a change in storage may be observed at hydraulic fracture closure. From the estimated formation properties, the methods may be useful for, among other things, determining whether a pre-existing fracture is damaged and evaluating the effectiveness of a previous fracturing treatment to determine whether a formation requires restimulation.

Methods and systems for determining reservoir properties of subterranean formations with pre-existing fractures

Methods and systems are provided for evaluating subsurface earth oil and gas formations. More particularly, methods and systems are provided for determining reservoir properties such as reservoir transmissibilities and average reservoir pressures of a formation layer or multiple layers using fracture-injection/falloff test methods. The methods herein may use pressure falloff data generated by the introduction of an injection fluid at a pressure above the formation fracture pressure in conjunction with a fracture-injection/falloff test model to analyze reservoir properties. The fracture-injection/falloff test model recognizes that a new induced fracture creates additional storage volume in the formation and that a fracture-injection/falloff test in a layer may exhibit variable storage during the pressure falloff, and a change in storage may be observed at hydraulic fracture closure.

Methods and systems for determining reservoir properties of subterranean formations

Compression and crushing behavior of ceramic proppants and sand under high stresses

Selecting Candidate Wells for Refracturing Using Production Data

This study presents a method to determine the present condition of a refracturing candidate gas well and allows the operator to decide if further stimulation is warranted. This method involves the use of type curves, computer analyses of the original treatment, and a logical comparison of the results. By using constant pressure and constant rate-type curves to analyze actual well performance and buildup data, the effective fracture lengths and fracture conductivities created by the original fracturing treatments were calculated. Computer analyses of these original treatments were calculated. Computer analyses of these original treatments were used to estimate created fracture lengths and, in conjunction with laboratory data, fracture flow capacities. A comparison of these fracture parameters allowed a better understanding of the current performance and resulted in successful refracturing treatments. Lack of agreement between type curves and computer analyses would have indicted potential problem areas, such as proppant transport or lack of fracture confinement.

A Diagnostic Technique For Restimulation Candidate Selection

The use of surfactants during various types of fracturing and acidizing treatments on oil wells is a commonly accepted practice. It is known and has been verified by several laboratory studies that surfactants have a marked effect on formation rock permeability in the treated wells. During hydraulic fracturing treatments, for example, large volumes of surfactant-bearing fluids are pumped deep into the formation matrix through the created fracture system. The results are presented of an investigation of the behavior of fluid flow on formation core plugs that have been subjected to either aqueous base fluids or hydrocarbon fluids containing various types of oil-wetting or water-wetting surfactants. Guide lines as to the most efficient types of workover fluid and surfactant combinations for maintaining hydrocarbon permeability are indicated from the data obtained. A method of water-block removal and restoring formation hydrocarbon permeability also has been observed and is discussed.

The Effect of Surfactant-Bearing Fluids on Permeability Behavior in Oil-Producing Formations

The objective of a hydraulic fracturing treatment is to place a conductive fracture deep into the producing formation. Fracture flow capacity, or ability of the propped fracture to conduct fluids, is one of the most important aspects of the treatment. Several laboratory test procedures have been developed to evaluate proppants under a wide range of closure pressures and concentrations. As well depths increase, it is necessary to adjust proppant systems to compensate for additional loads under producing conditions. Recently, success has been encountered using mixtures of sand and high strength proppants in deep formations in Northern Louisiana, East Texas, and Oklahoma. Information provided in this work will offer guidelines which should be considered for any fracturing treatment using propping agent. Fracture flow capacity of the fracture system is of utmost importance currently because many marginal zones are being completed and fractured. Sustained production increase is also very important. Laboratory and field application data indicate proppant systems initially selected have an influence on well production behavior throughout the producing life of the well.

Fracture Flow Capacity - A Key to Sustained Production after Hydraulic Fracturing

Large-volume fracturing treatments consisting of several hundred thousand gallons of fluid and very large quantities of sand are being conducted throughout the U.S. These treatments are conducted in an effort to provide sustained production increases from extensive, low-permeability reservoirs. Several such treatments have been conducted in the northeastern U.S. Application of the massive fracturing approach in this area is unique since the low reservoir temperatures, relatively low reservoir pressures, and formation types make fracturing fluid selection and treatment method primary considerations. This study describes from geology and laboratory tests the formations involved, types of treatments that have been conducted, and indicates preliminary results based on case histories. (10 refs.)

Alfred R. Jennings

Papers

A Diagnostic Technique For Restimulation Candidate Selection

The Effect of Surfactant-Bearing Fluids on Permeability Behavior in Oil-Producing Formations

Fracture Flow Capacity - A Key to Sustained Production after Hydraulic Fracturing

Massive Hydraulic Fracturing In The Eastern United States