This Well Header data set contains basic information describing well boreholes in Arizona associated with thermal properties. Each well header has a separate record (rows) for each well bore. The data set contains a total of 1,146 records.

This Geothermal Permitting Guide was created as a reference tool for geothermal stakeholders interested in developing low temperature direct use and/or power production projects. It addresses the environmental regulatory requirements beginning after acquisition of the land and/or mineral rights. Organized by development activity, it begins with resource exploration and continues to well abandonment and project closure. No one set of standard regulations applies to geothermal projects due to the differences in land and/or mineral rights ownership, location and resource chemistry. Geothermal resources in California occur in disparate environments from mountainous to desert terrains. The resource also differs from being liquid dominated high or low temperature to steam-dominated high temperature. Regional regulators such as counties, regional water quality control boards and air districts develop regulations based on the needs of their jurisdictions. The document contains websites and regulatory citations as statutes and regulations change.

PROGRAM HIGHLIGHTS: GEOTHERMAL DRILLING ACTIVITY In 2008, 32 new high-temperature geothermal wells were drilled in California compared to 12 wells drilled in 2007. Twenty- two of these wells were drilled in the Brawley field, 3 in the Salton Sea field and 7 at The Geysers (Figure 1). Total footage drilled in 2008 increased 5.7 times over the total footage drilled in 2007-- 194,758 feet ompared to 49,355 feet (Figure 2). The need for sustainable power set against the turmoil of the world’s economies created a chaotic 2008. What 2009 will bring in terms of developing geothermal projects is uncertain. However, one thing is certain, the increasing population’s need for electricity. This need alone would seem to indicate increased geothermal development in California especially in areas of known potential. GEOTHERMAL REGULATIONS The regulations used by Division staff to regulate geothermal wells in California were updated in 2008. Requirements were added for the maintenance of leases, well construction, spill contingency plans, and subsidence monitoring. Definitions were made clearer for observation wells and injection projects. CALIFORNIA ENVIRONMENTAL QUALITY ACT (CEQA) In 2008, no new applications were received. ENVIRONMENTAL AWARDS The Geysers Power Company, LLC (Calpine Corporation) received an award from the Department of Conservation for eight years of outstanding lease-enhancement activities at The Geysers Geothermal field. Mammoth Pacific also received an outstanding lease award for its maintenance of the Casa Diablo field.

This paper presents the initial results of a survey of the occurrence and characteristics of geopressured fluid resources in California using the publicly-available database involving more than 150,000 oil and gas wells drilled in the State. Of the 975 documented on-shore oil and gas pools studied, about 42% were identified as potentially geopressured. Geothermal gradients in California oil and gas fields lie within the normal range of 1°F to 2°F per 100 feet. Except for the Los Angeles Basin, there was no evidence of higher temperatures or temperature gradients in geopressured pools. The porosity of geopressured pools shows the same normal distribution as for normal pressured pools, with a mode in the range of 20 to 25%. The salinity distribution of both the geopressured and normal pressured pools appear to be bimodal, each with two peak ranges of 0 to 10,000 and 25,000 to 30,000 ppm.

This dataset contains active fault features compiled by the Arizona Geological Survey, and published as a Web feature service for the National Geothermal Data System. Fields in the Active Fault Feature Content Model will become XML elements in interchange documents for WMS simple features provided by a node in the USGIN network. Each feature includes a Fault Name, Symbol and Source. The dataset is spatially referenced to EPSG: 4326 (for interoperability). The data contained in the submitted dataset is available as an Excel Spreadsheet, Access Database (.mdb), ESRI service, WMS and WFS service. Link to Active (Quaternary) Fault Feature Content Model: http://stategeothermaldata.org/data_delivery/content_models/active_faultquaternary_fault.

This paper presents an analysis of the well productivity enhancement possible by drilling multi-legged (or “forked” or “multilateral”) wells in geothermal fields at temperatures in the 100 to 250°C range. A parameter, Productivity Enhancement Factor (“PEF”), is introduced to quantify productivity enhancement; it is defined as the ratio of the downhole productivity index of the multi-legged well to that of the original hole before the forked leg was added. Assuming the original hole to be vertical, it is shown that PEF rises sharply with deviation angle of the forked leg upto about 5 degrees; beyond this, PEF continues to increase with deviation angle albeit at a slower rate.

To prioritize information for archiving and to determine the applicability of the Fenton Hill experience to the future development of Enhanced Geothermal Systems (EGS), an integrated review was made of five categories of Fenton Hill information: hydraulic fracturing data, well logs, seismic data, flow test data and tracer test data. Major experiments were identified, the methods of data collection and analysis were determined, the location and format of the data were determined, and further analyses that would yield information of value to EGS developers were suggested. Such analyses would be directed toward the determination of: I) if and how the state of stress in the reservoir changed during sequential fracturing jobs; 2) how the orientation of fractures changed with depth and location; 3) how the reservoir size increased as fracturing and flow testing operations proceeded; 4) how the hydraulic properties and heat-transfer characteristics of the reservoir varied with changes in operating conditions; and 5) how the Phase II reservoir (the deeper and hotter of the two reservoirs developed) would behave over the long term under various operating conditions.

As part of the Desert Peak EGS project, tracer testing was conducted involving two existing injection wells at the Desert Peak geothermal field. The tracer data showed very strong returns from both injectors to one of the production wells, with much lower returns to the remaining producers. The tracer-swept pore volume was estimated using a first-moment analysis of the return-curve data.

The publicly available database on oil and gas fields in California provides a significant and consistent source of information which can be used to evaluate geopressure. A total of 410 pools have pressure gradients exceeding 0.45 psi/foot; these are considered to be potentially geopressured. At least 70 of these have pressures distinctly higher than predicted by the regional hydrostatic gradient, and 8 pools are super pressured.

In planning the development of a geothermal field, there is a trade-off between plant capacity and the cost of make-up drilling. A larger plant benefits from economies of scale in the construction and operation of surface facilities. On the other hand, a larger plant also places a greater load on the geothermal reservoir, which causes higher rates of decline in well productivity. Greater decline rates for existing wells require a larger number of make-up wells. Because the cost of make-up wells occurs later in the project life, this cost has relatively less impact on project economics than the up-front cost of plant construction. Similarly, the loss of revenue from a decline in output late in a project's life is much less significant than revenue foregone at the start of a project due to limited plant capacity.