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(open access)

Measurement of injectivity indexes in geothermal wells with two permeable zones

Injectivity tests in wells with two permeable zones and internal flow is analyzed in order to include the usually severe thermal transient effects. A theoretical analysis is performed and a method devised to obtain information from the thermal transient, provided that temperature is measured simultaneously with pressure. The technique is illustrated with two real tests performed at Miravalles, Costa Rica. It allows to estimate total injectivity index as well as the injectivity index of each one of the two zones separately. Correct position of measuring tools and nature of spontaneous internal flow is also discussed.

Date: January 20, 1994

Creator: Acuna, Jorge A.

Object Type: Article

System: The UNT Digital Library

(open access)

The Boerne Star (Boerne, Tex.), Vol. 90, No. 16, Ed. 1 Wednesday, April 20, 1994

Weekly newspaper from Boerne, Texas that includes local, state, and national news along with advertising.

Date: April 20, 1994

Creator: Aldridge, Leon

Object Type: Newspaper

System: The Portal to Texas History

(open access)

The Boerne Star (Boerne, Tex.), Vol. 90, No. 29, Ed. 1 Wednesday, July 20, 1994

Weekly newspaper from Boerne, Texas that includes local, state, and national news along with advertising.

Date: July 20, 1994

Creator: Aldridge, Leon

Object Type: Newspaper

System: The Portal to Texas History

(open access)

Results of injection and tracer tests in Olkaria East Geothermal Field

This paper presents results of a six month Injection and Tracer test done in Olkaria East Geothermal Field The Injection tests show that commencement of injection prior to onset of large drawdown in the reservoir leads to greater sustenance of well production and can reduce well cycling which is a common feature of wells in Olkaria East Field. For cases where injection is started after some drawdown has occurred in the reservoir, injection while leading to improvement of well output can also lead to increase in well cycling which is a non desirable side effect. Tracer tests reveal slow rate of fluid migration (< 5 m/hr). However estimates of the cumulative tracer returns over the period of injection is at least 31% which is large and reveals the danger of late time thermal drawdown and possible loss of production. It is shown in the discussion that the two sets of results are consistent with a reservoir where high permeability occurs along contact surfaces which act as horizontal "fractures" while the formations between the "fractures" have low permeability. This type of fracture system will lead to channeled flow of injected fluid and therefore greater thermal depletion along the fractures while formations …

Date: January 20, 1994

Creator: Ambusso, Willis J.

Object Type: Article

System: The UNT Digital Library

(open access)

Large-scale three-dimensional geothermal reservoir simulation on PCs

TOUGH2, Lawrence Berkeley Laboratory's general purpose simulator for mass and heat flow and transport was enhanced with the addition of a set of preconditioned conjugate gradient solvers and ported to a PC. The code was applied to a number of large 3-D geothermal reservoir problems with up to 10,000 grid blocks. Four test problems were investigated. The first two involved a single-phase liquid system, and a two-phase system with regular Cartesian grids. The last two involved a two-phase field problem with irregular gridding with production from and injection into a single porosity reservoir, and a fractured reservoir. The code modifications to TOUGH2 and its setup in the PC environment are described. Algorithms suitable for solving large matrices that are generally non-symmetric and non-positive definite are reviewed. Computational work per time step and CPU time requirements are reported as function of problem size. The excessive execution time and storage requirements of the direct solver in TOUGH2 limits the size of manageable 3-D reservoir problems to a few hundred grid blocks. The conjugate gradient solvers significantly reduced the execution time and storage requirements making possible the execution of considerably larger problems (10,000+ grid blocks). It is concluded that the current PCs provide …

Date: January 20, 1994

Creator: Antunez, Emilio; Moridis, George & Pruess, Karsten

Object Type: Article

System: The UNT Digital Library