^{1,2}

^{1,3}

^{1}

^{1}

^{2}

^{3}

The measures operation is an important component of borehole operation, and the operation effects directly affect the increase of oil and gas production. In perspective of the present reality of borehole operation company, the authors analyze the commonly used type of measures on the oil field, summarize six indicators to evaluate the measures operation effect, and give the quantitative calculation method for six evaluation indicators. Through the experts grading method, we can obtain all the weights of indicators and then establish the fuzzy comprehensive evaluation model of operation effect of measures. The evaluation model can be used to evaluate the operation effect of single well, oil block, or the branch company. Based on the actual data of measures operation of a branch company, using the fuzzy comprehensive evaluation approach to evaluate each block in the branch company, this paper obtained the same conclusion as the qualitative analysis.

Petroleum and natural gas are two kinds of important resources in people’s material lives and the development process of human civilization. The oil and gas resources in the underground are exploited by way of drilling. But, in the long-term production process, oil-water wells suffer damage from the flow of oil and gas without a break and also from the workover operation in order to maintain normal production and the alteration measures of oil layer in order to enhance oil recovery, which make oil wells change every moment and gradually age, and various types of faults occur, eventually resulting in the fact that the production of oil wells cannot be normal, or is even stop production. Therefore, we must take the borehole operation for the oil-water wells with problems and faults to make the oil wells resume normal production. This means that the borehole operation is an important technology in ensuring the normal production of oil-water wells in the process of oil field development. Moreover, the measures operation is a deciding factor in increasing the production of oil and gas. Currently, the verbal description is the main method to evaluate operation effects in the borehole operation; this only stays on the level of qualitative analysis, and different borehole operation companies for the emphasis on the operation effects are not the same. The most concern for the oil-field companies is the output of oil and gas, and the factors affecting the output of oil and gas are largely determined by the measures of increasing production and injection. Accordingly, this paper analyzes these measures commonly used in oil fields and sums up the evaluation indicators for evaluating the measure effects. According to the daily data record about the measure operation in a borehole operation company, the fuzzy comprehensive evaluation method can be used to evaluate the operation effects of measures. Assume that

In the process of oil-field development, we often meet with some low-permeability reservoirs; even under a larger differential pressure, it is also difficult to obtain high output. And some reservoirs in the drilling process are invaded by drilling fluid, so it will lower the reservoir permeability near the bottom of well, and then lead to decline the oil output. In addition, oil-water wells in the process of production, due to various reasons, will also be blocked near the bottom, making the injected volume for water injection wells and the oil output for oil wells, thus affecting the mining speed and the recovery rate. In these cases, we must implement all kinds of measures to improve these problem reservoirs or wells on oil-field.

On the oil field, the commonly used stimulation measures mainly include hydraulic fracturing, acidizing, sand prevention, water plugging, secondary solidification, sealing channeling [

From the point of view of evaluation, we can evaluate from single well a block or the whole oil company and also from single measures or multiple measures. If we evaluate the single measures of an oil well, the workload is very large, because thousands of wells need to be repaired every year for a borehole operation company, and a well may need to use more than one kind of measures simultaneously. Therefore, this paper conducts the effect evaluation in units of blocks. Assume there are

The incremental output of oil is divided into the net incremental oil output (

The period of validity is defined as

The effective rate of measures is defined as

The construction period is defined as

The incremental volume of water injection is defined as

Considering the actual situation of different blocks, this paper adopts the percentage of reduced value of water injection pressure to compare each block. The reduced value of water injection pressure is defined as

The importance of different indicators is different in the scheme evaluation, and the measures we describe the size of the importance for an indicator are called the weight of the indicator. The indicator weight is one kind of comprehensive measure including both subjective evaluation and objective expression, reflecting the relative importance between indicators. At present, there have been dozens of methods to determine the weights of indicators [

Assume that the

The quantity scale of 0.1~0.9.

Scale value | Definition | Explanation |
---|---|---|

0.5 | Equally important | Two elements compared, equally important. |

0.6 | Slightly important | Two elements compared, an element is more slightly important than another element. |

0.7 | Obviously important | Two elements compared, an element is more obviously important than another element. |

0.8 | Much more important | Two elements compared, an element is much more important than another element. |

0.9 | Extremely important | Two elements compared, an element is more extremely important than another element. |

0.1, 0.2, 0.3, 0.4 | Converse comparison | If |

Assume that the grading value of the

The grading values of

Indicator | Indicator | Indicator | Indicator | Indicator | Indicator | |
---|---|---|---|---|---|---|

Expert 1 | ||||||

Expert 2 | ||||||

Expert |

The weights can be obtained by means of the following expression:

The fuzzy comprehensive evaluation method is a kind of evaluation method with combining fuzzy theory and mathematical model. According to the given evaluation criteria and the measured values, by means of the fuzzy transformation, we can make evaluation of things. The specific evaluation steps are as follows.

Determine the indicator set of operation evaluation of measures

Determine the ranking set of operation effect

Determine the weights of all the evaluation indicators

Write out the evaluation matrix

Establish the fuzzy evaluation model:

Calculate the evaluation values of indicators

The above evaluation matrix

Assume that there are

When the

When the

In the above-mentioned six indicators, the incremental output of oil and gas, the period of validity, the effective rate, and the incremental volume of water injection are the benefit type, while the construction period and the water injection pressure are the cost type. By (

According to the grading values given by experts, through (

The operation data of measures of a borehole operation company in 2010 is as follows.

Crude oil production is 4.78 million tons, 275600 tons of which is the incremental production of measures. All measures are 696 times, and the effective measures are 561 times. The period of validity of measures is 289 days, and the average construction period for measures is 7 days. In 2010, the total volume of water injection is 39.41 million cubic meters, compared with 2009, more than 2.56 million cubic meters. The average injection pressure of 2010 is 24 MPa, and in 2009 the average water pressure is 31 MPa.

Through the experts grade, the weight vector of indicators is decided by

Relative incremental oil production of measures:

Period of validity:

Effective rate:

Average construction period:

Relative incremental volume of water injection:

Relative drop pressure of water injection:

Through the random survey for these on-site oil workers, we acquire the following evaluation matrix:

In this paper, we establish the fuzzy comprehensive evaluation model to evaluate the effect of measures operation for the oil-water well. It is favorable to solve the evaluation problem about the operation effect of measures and also provide a reference for the downhole operation company in decision making. First of all, we analyze the effect factors of measures operation in the process of oil-field development and put forward six indicators to evaluate the operation effect of measures. Secondly, we present a kind of new method to determine the weights of evaluation indicators. Then, summarize the steps to evaluate the operation effect of measures. Finally, based on the actual data of measures operation of a branch company, using the fuzzy comprehensive evaluation method to evaluate the operation effect of measures, this paper obtains the same conclusion as the qualitative analysis.

Thanks are due to the support by National Natural Science Foundation of China (no. 50874094).