VAPLIQ MODEL OF THE LOS AZUFRES GEOTHERMAL SYSTEM
tem (natural state), and on its basis concluded that a substantial we revise and expand our previous vapvertical permeability contrast must liq model of the Los Azufres hydrotherexist between the vaporand the limal system. We present data that delinquid-dominated layer, the smaller pereate the vertical distributions of the meability corresponding to the later. formation's thermal conductivity and Assuming a homogeneous vertical disbulk density. Both distributions distribution of thermal conductivity we close a sharp change of formation propestimated permeability values and other erties at the boundary between the thermohydrological parameters of the liquid-dominated layer and the steam cap. This supports the inference of our previous work that a substantial perthis model was consistent with a meability contrast must exist between number of observations (downhole presthe liquidand vapor-dominated layers sures, stabilized temperatures, geotheof the system. we present the observed rmometrical estimates, hydrother-mal vertical distribution of liquid saturaalteration as deduced from drill cutttion in the system as inferred from the ings, and the ranges of permeabi-lity chemical composition of reservoir fluand thermal conductivity found in laboids and well logs; we use it, in addiratory measurements of drill cores), tion to the pressure profile, to calibthe reliability ef the estimates remairate the model's thermophysical paramened somewhat questionable because: (a ) ters. Calibration against both observed only the observed vertical pressure profiles greatly improves the reliabilprofile was fitted in detail, and it is , ity of the model. The new model prediknown that pressure fitting alone may cts vertical pe about 0.1~10 l8 m tem. In addition to the d vertical permeability, th des estimates of the fluxes and of the relativ functions of the system 1988a, 1988b) we otherma1 systems a gical conditions (The central, upfl systems is a sta liquid layer at dominated zone vapor-dominated cap). We also presented a vapliq model of the Los Azufres sysand Arellano 1988a, 1988b) we assume a step distribution of vertical pemeabi-
EVIDENCE OF TWO EXTREME FLOW REGIMES OPERATING I N THE PRODUCTION ZONE OF DIFFERENT WELLS FROM LOS AZUFRES
A published method for calculating excess steam is modified in order to make it applicable to the case of a well producing fluid with a high non-condensable gas content. The method is applied to data from a number of wells from Los Azufres. The results show the expected linear relation between excess steam and the molar fraction of CO{sub 2} in the total discharge. The modified method also provides an estimate for the molar fraction of CO{sub 2} in the liquid phase of the reservoir. It is found that this concentration is relatively homogeneous in the southern section of the field, and seems to be slightly smaller in the deeper zones of the northern section. The calculated values of excess steam agree qualitatively, but not quantitatively, with values of steam quality in the undisturbed reservoir calculated by other authors. The calculation of excess steam tends to overestimate steam quality in cases where steam saturation in the reservoir is low, and has the opposite tendency when the steam quality in the reservoir is high. The first type of deviation is explained in terms of the effects of higher mobility of steam in the two-phase zone induced by pressure drawdown. The second type of deviation is explained as the result of boiling of liquid phase, and the consequent addition of (non-condensable) gas-poor steam to the flowing mass, also caused by the pressure drawdown. A necessary extension of the reasoning leading to these explanations, is the prediction that the non-condensable gas content in fluids produced from a reservoir with a high steam saturation, will either remain stable or decrease with time during exploitation.
The Inca Occupation of the South Coast of Peru
like the others, however; it forks into several nearly parallel ravines of which the largest are Huayuri, Rio Grande-Palpa, Ingenio (called Collao in ancient times), Nasca proper (the ancient Caxamarca), Taruga, and Poroma. Due to peculiarities of the local topography, the irrigated areas in Ica and the ravines of Nasca are located inland, at the foot of the mountains, rather than at the mouths of the rivers as is more usual in Peruvian coastal valleys. No sharp natural or cultural boundary separates the valley of Chincha from the valleys of Cafiete (ancient Huarco and Runahuana), Asia, and Mala, the next valleys going up the coast to the northwest. At the other end of the area we are considering, however, there is a sharp break; beyond Yauca the Andean foothills reach out to the sea, natural conditions are quite different, and there are important differences in the archaeological picture as well. The historical sources which mention the south coast are not particularly helpful, except in so far as they provide us with a few dates. To begin with, no chronicler gives an explicit account of the political organization of the south coast at the time it came into contact with the Incas. It can, perhaps, be inferred from Cabello Balboa's statements about common policy toward the Inca invaders that there was some sort of political connection between the valleys of Mala, Cafiete, and Chincha, but the connection need have been no more than a temporary military alliance. Cabello makes no mention at all of Pisco. The valleys of Ica, Nasca, and 125