The Amistad field in the Guayaquil Gulf in Ecuador, located at the east of the Nazca subduction zone with the South America plate, and at the west of the Andes Mountains, is in a zone suffering from an intense tectonic activity. It is divided into various structural block very heterogeneous in term of hydrocarbon content. Since the beginning of the development of this gas field in the shallow water of the Gulf of Guayaquil, various challenges has been encountered. Certain drilled wells gave unsatisfactory production test and the project economics has been questioned, meanwhile the Ecuadorian industry gas demand is increasing. Today it becomes critical to reach the production objectives. An unclear identification of the sand bodies due to a poor log signature, a difficult estimation of the water saturation and a challenging quantification of the irreducible and clay bound water volumes with conventional logs lead in some cases to water production. A tailor-made workflow focusing on resolving these challenges has been built. The use of spectroscopy measurements, when available, permits to identify masked sand bodies. Its integration with triaxial resistivity tools permits to identify gas-bearing low resistivity zones and estimate the water saturation, while the nuclear magnetic resonance permits to quantify the amount of non-movable water. This new methodology shows a significant improvement of the understanding of the reservoir in the new drilled wells, but how to populate this information acquired with modern technology to the old wells? A method using the nuclear magnetic resonance information from the new wells in combination with the effective porosity per electro-facies permitted to populate a model through the whole field. It permits to solve for the irreducible water saturation, one of the most critical information in this field. The production results on the last three wells where this methodology has been applied are a clear indicator of the success of this workflow leading to production well test a lot above the expected one, meanwhile the production behavior of the older wells is now well understood.

The Amistad field in the Ecuadorian Gulf of Guayaquil has been producing dry gas since 2002 from the productive formation Subibaja. This field covers an area of 2,250 km 2 and is located offshore about 100 km southwest of the city of Guayaquil. Six wells in the field produce 60 MMSCFD and 940 BWPD. Gas production from this field is affected by water production and reservoir pressure declination. In particular, liquid-loading is considered a critical problem in the gas wells productivity, with water intrusion occurring in the wellbores during temporary shut-in for workover operations.A coiled tubing (CT) velocity string is a known method to unload liquids in gas wells; the correct choice of CT size may optimize gas well productivity. The smaller-diameter CT is installed inside the production tubing to improve gas velocity, thereby avoiding water column accumulation at the bottom of the well.The reservoir inflow performance relationship (IPR) and tubing performance relationship (TPR) are considerations in velocity string design. Both curves are independent and their intersection, compared with the minimum gas flow rate on a J-curve, indicates whether liquid loading will occur in a gas well. This paper discusses the technical concepts of velocity string design, as well as simulations and analysis for a case history of deploying velocity string technology in a gas well with optimal results.

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The challenges presented by a field in Ecuador included placing the wells in the cleanest, most permeable portion of the reservoir, in the middle of the structure, without penetrating an overlaying kaolinitic bed or the caprock shale above the reservoir or penetrating the water bearing zone. These objectives could not be optimally achieved with traditional wellbore imaging sensors or with deep non-azimuthal wave resistivity. Wellbore imaging instruments identify the relative dip and azimuth of geological events intersecting the wellbore, but the information is clear only after leaving the reservoir. Nonazimuthal wave resistivity predicts the impending intersection with a reservoir boundary, but does not predict the azimuth of approach. In the first instance, a proper decision can be made only after exiting the reservoir; in the second instance, a proper decision requires other knowledge about the probable direction of the approaching boundary.A newly deployed azimuthal deep resistivity while-drilling sensor produces a vast array of azimuthal measurements. When mapped into an image, deep resistivity behaves for the most part like traditional images in which "smiling" patterns indicate that the wellbore is going up stratigraphically and "frowning" patterns indicate that the wellbore is going down stratigraphically. One exception is the newly discovered phenomenon of the "bright spot" that appears when approaching a low resistivity shale or water bearing interval from a high resistivity reservoir. The bright spot clearly indicates an impending reservoir exit. Because it is keyed to the low side of the well, the bright spot indicates the direction of the required evasive action to remain within the desired interval. This visual indicator is complemented by a novel quantitative measurement, the Geosignal, which features a strong exponential dependence on the distance to the boundary of the reservoir. In the examples shown, the visual information from the bright spot is combined with the quantitative information from the Geosignal measurement to properly guide real-time geosteering decisions.